U.S. patent application number 10/615995 was filed with the patent office on 2004-04-29 for electron-emitting device, electron source, and image-forming apparatus.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Banno, Yoshikazu, Mitome, Masanori, Nomura, Ichiro, Ohnishi, Toshikazu, Ono, Takeo, Suzuki, Hidetoshi, Yamanobe, Masato.
Application Number | 20040082249 10/615995 |
Document ID | / |
Family ID | 27472054 |
Filed Date | 2004-04-29 |
United States Patent
Application |
20040082249 |
Kind Code |
A1 |
Ohnishi, Toshikazu ; et
al. |
April 29, 2004 |
Electron-emitting device, electron source, and image-forming
apparatus
Abstract
An electron-emitting device comprises a pair of oppositely
disposed electrodes and an electroconductive film arranged between
the electrodes and including a high resistance region. The high
resistance region has a deposit containing carbon as a principal
ingredient. The electron-emitting device can be used for an
electron source of an image-forming apparatus of the flat panel
type.
Inventors: |
Ohnishi, Toshikazu; (Tokyo,
JP) ; Yamanobe, Masato; (Tokyo, JP) ; Nomura,
Ichiro; (Kanagawa-Ken, JP) ; Suzuki, Hidetoshi;
(Kanagawa-Ken, JP) ; Banno, Yoshikazu;
(Kanagawa-Ken, JP) ; Ono, Takeo; (Tokyo, JP)
; Mitome, Masanori; (Kanagawa-Ken, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Assignee: |
CANON KABUSHIKI KAISHA
TOKYO
JP
|
Family ID: |
27472054 |
Appl. No.: |
10/615995 |
Filed: |
July 10, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10615995 |
Jul 10, 2003 |
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09332101 |
Jun 14, 1999 |
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09332101 |
Jun 14, 1999 |
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08264497 |
Jun 23, 1994 |
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6169356 |
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Current U.S.
Class: |
445/6 |
Current CPC
Class: |
H01J 1/316 20130101;
H01J 9/027 20130101 |
Class at
Publication: |
445/006 |
International
Class: |
H01J 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 27, 1993 |
JP |
5-331103 |
Dec 28, 1993 |
JP |
5-335925 |
Jun 20, 1994 |
JP |
6-137317 |
Claims
What is claimed is:
1. An electron-emitting device comprising a pair of oppositely
disposed electrodes and an electroconductive film arranged between
the electrodes and including a high resistance region,
characterized in that the high resistance region has a deposit
containing carbon as a principal ingredient.
2. An electron-emitting device according to claim 1, wherein said
deposit containing carbon as a principal ingredient is also present
in the vicinity of said high resistance region.
3. An electron-emitting device according to claim 2, wherein said
deposit containing carbon as a principal ingredient is present on
said electroconductive film from part of said high resistance
region.
4. An electron-emitting device according to claim 3, wherein said
deposit containing carbon as a principal ingredient is present
particularly on one of said electrodes from said high resistance
region.
5. An electron-emitting device according to claim 4, wherein said
deposit containing carbon as a principal ingredient is present
particularly on part of the electroconductive film close to the
higher potential one of said electrodes from said high resistance
region.
6. An electron-emitting device according to claim 1, wherein said
electroconductive film is made of electroconductive fine
particles.
7. An electron-emitting device according to claim 6, wherein said
electroconductive fine particles are made of metal or an oxide of
metal.
8. An electron-emitting device according to claim 6, wherein at
least part of said electroconductive fine particles are coated with
said deposit.
9. An electron-emitting device according to claim 1, wherein said
high resistance region contains electroconductive fine
particles.
10. An electron-emitting device according to claim 9, wherein at
least part of said electroconductive fine particles are coated with
said deposit.
11. An electron-emitting device according to claim 1, wherein at
least part of said electrodes are coated with said deposit
containing carbon as a principal ingredient.
12. An electron-emitting device according to claim 1, wherein said
deposit containing carbon as a principal ingredient is principally
made of graphite, amorphous carbon or a mixture thereof.
13. An electron-emitting device according to claim 1, wherein the
electron emission current of the device has a monotonically
increasing characteristic relative to the voltage applied to said
electrodes.
14. An electron source comprising an electron-emitting device for
emitting electrons according to input signals, characterized in
that said electron-emitting device is a device according to one of
claims 1 through 13.
15. An electron source according to claim 14, wherein it comprises
a plurality of said electron-emitting devices arranged in a
plurality of rows, each of said electron-emitting devices being
connected to wirings at opposite ends, and a modulation means for
modulating electron beams emitted from said electron-emitting
devices.
16. An electron source according to claim 14, wherein it comprises
a plurality of said electron-emitting devices arranged in rows and
respectively connected to m X-directional wirings and n
Y-directional wirings that are mutually electrically insulated.
17. An image-forming apparatus comprising an electron source and an
image-forming member for forming images according to input signals
characterized in that said electron source comprises an
electron-emitting device according to one of claims 1 through
13.
18. An image-forming apparatus according to claim 17, wherein said
electron source comprises a plurality of said electron-emitting
devices arranged in a plurality of rows, each of said
electron-emitting devices being connected to wirings at opposite
ends, and a modulation means for modulating electron beams emitted
from said electron-emitting devices.
19. An image-forming apparatus according to claim 17, wherein said
electron source comprises a plurality of said electron-emitting
devices arranged in rows and respectively connected to m
X-directional wirings and n Y-directional wirings that are mutually
electrically insulated.
20. An image-forming apparatus according to claim 17, wherein the
emission current and the device current of said electron source
have a monotonically increasing characteristic relative to the
voltage applied to said devices.
21. An image-forming apparatus according to claim 17, wherein the
inside of said image-forming apparatus is maintained to a degree of
vacuum that does not allow any additional deposition to be made to
said deposit containing carbon as a principal ingredient.
22. A method of manufacturing an electron-emitting device
comprising a pair of oppositely disposed electrodes and an
electroconductive film arranged between the electrodes,
characterized in that it comprises a device activation process.
23. A method of manufacturing an electron-emitting device according
to claim 22, wherein said activation process is a process for
depositing a deposit containing carbon as a principal ingredient on
said electroconductive film.
24. A method of manufacturing an electron-emitting device according
to claim 23, wherein said activation process comprises a step of
applying a voltage to the electroconductive film arranged between
the electrodes in vacuum.
25. A method of manufacturing an electron-emitting device according
to claim 24, wherein said voltage is applied in the form of
pulse.
26. A method of manufacturing an electron-emitting device according
to claim 25, wherein said voltage is above a
voltage-controlled-negative-res- istance level.
27. A method of manufacturing an electron-emitting device according
to claim 26, wherein said voltage is a drive voltage for driving
the electron-emitting devices.
28. A method of manufacturing an electron-emitting device according
to claim 23, wherein said activation process comprises a step of
applying a voltage to the electroconductive film arranged between
the electrodes in an atmosphere containing an introduced carbon
compound.
29. A method of manufacturing an electron-emitting device according
to claim 28, wherein said voltage is applied in the form of
pulse.
30. A method of manufacturing an electron-emitting device according
to claim 29, wherein said voltage is above a
voltage-controlled-negative-res- istance level.
31. A method of manufacturing an electron-emitting device according
to claim 30, wherein said voltage is a drive voltage for driving
the electron-emitting devices.
32. A method of manufacturing an electron-emitting device according
to claim 28, wherein said carbon compound is an organic gas.
33. Method of manufacturing an electron-emitting device according
to claim 32, wherein said organic gas has a vapor pressure of not
higher than 5,000 hPa at the temperature and in the atmosphere of
the activation process.
34. A method of manufacturing an electron-emitting device according
to claim 33, wherein said organic gas has a vapor pressure of not
higher than 5,000 hPa at 20.degree. C.
35. A method of manufacturing an electron-emitting device according
to claim 32, wherein said organic gas has a vapor pressure between
0.2 hPa and 5,000 hPa at the temperature and in the atmosphere of
the activation process.
36. A method of manufacturing an electron-emitting device according
to claim 35, wherein said organic gas has a vapor pressure between
0.2 hPa and 5,000 hPa at 20.degree. C.
37. A method of manufacturing an electron-emitting device according
to claim 22, wherein it further comprises a forming process.
38. A method of manufacturing an electron-emitting device according
to claim 37, wherein said forming process is a step of forming a
high resistance region in the electronconductive film arranged
between the electrodes.
39. A method of manufacturing an electron-emitting device according
to claim 22, wherein said activation process is carried out after
said forming process.
40. An electron source comprising an electron-emitting device for
emitting electrons according to input signals, characterized in
that said electron-emitting device is manufactured by a method
according to one of claims 22 through 39.
41. An electron source according to claim 40, wherein it comprises
a plurality of said electron-emitting devices arranged in a
plurality of rows, each of said electron-emitting devices being
connected to wirings at opposite ends, and a modulation means for
modulating electron beams emitted from said electron-emitting
devices.
42. An electron source according to claim 40, wherein it comprises
a plurality of said electron-emitting devices arranged in rows and
respectively connected to m X-directional wirings and n
Y-directional wirings that are mutually electrically insulated.
43. An image-forming apparatus comprising an electron source and an
image-forming member for forming images according to input signals
characterized in that said electron source comprises an
electron-emitting device manufactured by a method according to one
of claims 22 through 39.
44. An image-forming apparatus according to claim 43, wherein said
electron source comprises a plurality of said electron-emitting
devices arranged in a plurality of rows, each of said
electron-emitting devices being connected to wirings at opposite
ends, and a modulation means for modulating electron beams emitted
from said electron-emitting devices.
45. An image-forming apparatus according to claim 43, wherein said
electron source comprises a plurality of said electron-emitting
devices arranged in rows and respectively connected to m
X-directional wirings and n Y-directional wirings that are mutually
electrically insulated.
46. An image-forming apparatus according to claim 43, wherein the
emission current and the device current of said electron source
have a monotonically increasing characteristic relative to the
voltage applied to said devices.
47. An image-forming apparatus according to claim 43, wherein the
inside of said image-forming apparatus is maintained to a degree of
vacuum that does not allow any additional deposition to be made to
said deposit containing carbon as a principal ingredient.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to an electron source and an
image-forming apparatus such as a display apparatus incorporating
an electron source and, more particularly, it relates to a novel
surface conduction electron-emitting device as well as a novel
electron source and an image-forming apparatus such as a display
apparatus incorporating such an electron source.
[0003] 2. Related Background Art
[0004] There have been known two types of electron-emitting device;
the thermoelectron type and the cold cathode type. Of these, the
cold cathode type include the field emission type (hereinafter
referred to as the FE-type), the metal/insulation layer/metal type
(hereinafter referred to as the MIM-type) and the surface
conduction type.
[0005] Examples of the FE electron-emitting device are described in
W. P. Dyke & W. W. Dolan, "Field emission", Advance in Electron
Physics, 8, 89 (1956) and C. A. Spindt, "PHYSICAL Properties of
thin-film field emission cathodes with molybdenum cones", J. Appl.
Phys., 47, 5284 (1976).
[0006] MIM devices are disclosed in papers including C. A. Mead,
"The tunnel-emission amplifier", J. Appl. Phys., 32, 646 (1961).
Surface-conduction electron-emitting devices are proposed in papers
including M. I. Elinson, Radio Eng. Electron Phys., 10 (1965).
[0007] An SCE device is realized by utilizing the phenomenon that
electrons are emitted out of a small thin film formed on a
substrate when an electric current is forced to flow in parallel
with the film surface. While Elinson proposes the use of SnO.sub.2
thin film for a device of this type, the use of Au thin film is
proposed in [G. Dittmer: "Thin Solid Films", 9, 317 (1972)] whereas
the use of In.sub.2O.sub.3/SnO.sub.2 and that of carbon thin film
are discussed respectively in [M. Hartwell and C. G. Fonstad: "IEEE
Trans. ED Conf.", 519 (1975)] and [H. Araki et al.: "Vacuum", Vol.
26, No. 1, p. 22 (1983)].
[0008] FIG. 27 of the accompanying drawings schematically
illustrates a typical surface-conduction electronemitting device
proposed by M. Hartwell. In FIG. 27, reference numeral 1 denotes a
substrate. Reference numeral 2 denotes an electrically conductive
thin film normally prepared by producing an H-shaped thin metal
oxide film by means of sputtering, part of which eventually makes
an electron-emitting region 3 when it is subjected to an
electrically energizing process referred to as "electric forming"
as described hereinafter. In FIG. 27, the thin horizontal area of
the metal oxide film separating a pair of device electrodes has a
length L of 0.5 to 1 mm and a width W of 0.1 mm. Note that the
electron-emitting region 3 is only very schematically shown because
there is no way to accurately know its location and contour.
[0009] As described above, the conductive film 2 of such a surface
conduction electron-emitting device is normally subjected to an
electrically energizing preliminary process, which is referred to
as "electric forming", to produce an electron emitting region 3. In
the electric forming process, a DC voltage or a slowly rising
voltage that rises typically at a rate of 1 V/min. is applied to
given opposite ends of the conductive film 2 to partly destroy,
deform or transform the thin film and produce an electron-emitting
region 3 which is electrically highly resistive. Thus, the
electron-emitting region 3 is part of the conductive film 2 that
typically contains fissures therein so that electrons may be
emitted from those fissures. The film 2 containing an
electron-emitting region that has been prepared by electric forming
is hereinafter referred to as a thin film 4 inclusive of an
electron-emitting region. Note that, once subjected to an electric
forming process, a surface conduction electron-emitting device
comes to emit electrons from its electron-emitting region 3
whenever an appropriate voltage is applied to the thin film 4
inclusive of the electron-emitting region to make an electric
current run through the device.
[0010] Known surface conduction electron-emitting devices having a
configuration as described above are accompanied by various
problems, which will be described hereinafter.
[0011] Since a surface conduction electron-emitting device as
described above is structurally simple and can be manufactured in a
simple manner, a large number of such devices can advantageously be
arranged on a large area without difficulty. As a matter of fact, a
number of studies have been made to fully exploit this advantage of
surface conduction electron-emitting devices. Applications of
devices of the type under consideration include charged electron
beam sources and electronic displays. In typical examples of
application involving a large number of surface conduction
electron-emitting devices, the devices are arranged in parallel
rows to show a ladder-like shape and each of the devices are
respectively connected at given opposite ends with wirings (common
wirings) that are arranged in columns to form an electron source
(as disclosed in Japanese Patent Application Laid-open Nos.
64-31332, 1-283749 and 1-257552). As for display apparatuses and
other image-forming apparatuses comprising surface conduction
electron-emitting devices such as electronic displays, although
flat-panel type displays comprising a liquid crystal panel in place
of a CRT have gained popularity in recent years, such displays are
not without problems. One of the problems is that a light source
needs to be additionally incorporated into the display in order to
illuminate the liquid crystal panel because the display is not of
the so-called emission type and, therefore, the development of
emission type display apparatuses has been eagerly expected in the
industry. An emission type electronic display that is free from
this problem can be realized by using a light source prepared by
arranging a large number of surface conduction electron-emitting
devices in combination with fluorescent bodies that are made to
shed visible light by electrons emitted from the electron source
(See, for example, U.S. Pat. No. 5,066,883).
[0012] In a conventional light source comprising a large number of
surface conduction electron-emitting devices arranged in the form
of a matrix, devices are selected for electron emission and
subsequent light emission of fluorescent bodies by applying drive
signals to appropriate row-directed wirings connecting respective
rows of surface conduction electron-emitting devices in parallel,
column-directed wirings connecting respective columns of surface
conduction electron-emitting devices in parallel and control
electrodes (or grids arranged within a space separating the
electron source and the fluorescent bodies along the direction of
the columns of surface conduction electron-emitting devices of a
direction perpendicular to that of the rows of devices (See, for
example, Japanese Patent Application Laid-open No. 1-283749).
[0013] However, little has been known about the behavior in vacuum
of a surface conduction electron-emitting device to be used for an
electron source and an image-forming apparatus incorporating such
an electron source and, therefore, it has been desired to provide
surface conduction electron-emitting devices that have stable
electron-emitting characteristics and hence can be operated
efficiently in a controlled manner. The efficiency of a surface
conduction electron-emitting device is defined for the purpose of
the present invention as the ratio of the electric current running
between the pair of device electrodes of the device (hereinafter
referred to device current If) to the electric current produced by
the emission of electrons into vacuum (hereinafter referred to
emission current Ie). It is desired to have a large emission
current with a small device current.
[0014] The inventors of the present invention who have long been
engaged in the study of this technological field strongly believe
that contaminants excessively deposited on and near the
electron-emitting region of a surface conduction electron-emitting
device can deteriorate the performance of the device, that
contaminants are mainly decomposition products of oil in the
evacuation system used for the device and that such deterioration
can be prevented if the electron-emitting region is controlled in
terms of shape, material and composition.
[0015] Thus, a low electricity consuming high quality image-forming
apparatus typically comprising an image-forming member of
fluorescent bodies can be realized if there provided a surface
conduction electron-emitting device that has stable
electron-emitting characteristics and hence can be operated
efficiently in a controlled manner. Such an improved image-forming
apparatus may be a very flat television set. A low energy consuming
image-forming apparatus may require less costly drive circuits and
other related components.
SUMMARY OF THE INVENTION
[0016] In view of the above described circumstances, it is
therefore an object of the present invention to provide a novel and
highly efficient electron-emitting device that has stable
electron-emitting characteristics with a low device current level
and a high emission current and hence can be operated efficiently
in a controlled manner and a novel method of manufacturing the same
well as a novel electron source incorporating such an
electron-emitting and an image-forming apparatus such as a display
apparatus using such an electron source.
[0017] According to an aspect of the invention, the above object
and other objects of the invention are achieved by providing an
electron-emitting device comprising a pair of oppositely disposed
electrodes and an electroconductive film arranged between the
electrodes and including a high resistance region, characterized in
that the high resistance region has a deposit containing carbon as
a principal ingredient.
[0018] According to another aspect of the invention, there is
provided a method of manufacturing an electron-emitting device
comprising a pair of oppositely disposed electrodes and an
electroconductive film arranged between the electrodes and
including a high resistance region, characterized in that it
comprises a step of activating the device.
[0019] According to still another aspect of the invention, there is
provided an electron source comprising an electron-emitting device
for emitting electrons as a function of input signals characterized
in that said electron-emitting device is produced with the above
described method.
[0020] According to a further aspect of the invention, there is
provided an image-forming apparatus comprising an electron source
and an image-forming member for forming images as a function of
input signals characterized in that said electron source comprises
an electron-emitting device that is produced with the above
described method.
[0021] Now, the present invention will be described in greater
detail by referring to the accompanying drawings that illustrate
preferred embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIGS. 1A and 1B are schematic plan and sectional side views
showing the basic configuration of a flat type surface conduction
electron-emitting device according to the invention.
[0023] FIGS. 2A through 2C are schematic side views showing
different steps of a method of manufacturing a surface conduction
electron-emitting device according to the invention.
[0024] FIG. 3 is a block diagram of a gauging system for
determining the performance of a surface-conduction type
electron-emitting device according to the invention.
[0025] FIGS. 4A through 4C are graphs showing voltage waveforms
observed during an electrically energizing process conducted on a
surface conduction electron-emitting device according to the
invention.
[0026] FIG. 5 is a graph showing the relationship between the
device current and the time of activation process.
[0027] FIGS. 6A and 6B are schematic sectional views showing an
embodiment of surface conduction electron-emitting device according
to the invention before and after an activation process
respectively.
[0028] FIG. 7 is a graph showing the relationship between the
device voltage and the device current as well as the relationship
between the device voltage and the emission current of an
embodiment of surface conduction electron-emitting device according
to the invention.
[0029] FIG. 8 is a schematic plan view of the substrate of an
embodiment of electron source according to the invention used in
Example 2 as described hereinafter, showing in particular the
simple matrix configuration of the substrate.
[0030] FIG. 9 is a schematic perspective view of the substrate of
the embodiment of electron source of FIG. 8.
[0031] FIGS. 10A and 10B are enlarged schematic plan views of two
different fluorescent layers that can be used alternatively for the
embodiment of FIG. 8.
[0032] FIG. 11 is a plan view of the electron source used in
Example 1 as described hereinafter.
[0033] FIG. 12 is a block diagram of the system used for the
activation process of Example 3 as described hereinafter.
[0034] FIG. 13 is an enlarged schematic partial plan view of the
substrate of the electron source of an embodiment of image-forming
apparatus according to the invention used in Example 2 as described
hereinafter.
[0035] FIG. 14 is an enlarged schematic sectional side view of the
substrate of FIG. 13 taken along line A-A'.
[0036] FIGS. 15A through 15D and 16E through 16H are schematic
partial sectional side views of the substrate of FIG. 13, showing
different steps of the method of manufacturing the same.
[0037] FIGS. 17 and 18 are schematic plan views of two different
substrates of electron source alternatively used in the
image-forming apparatus of Example 9.
[0038] FIGS. 19 and 22 are schematic perspective views of two
different panels alternatively used in the image-forming apparatus
of Example 9.
[0039] FIGS. 20 and 23 are block diagrams of two different electric
circuits alternatively used to drive the image-forming apparatus of
Example 9.
[0040] FIGS. 21A through 21F and 24A through 24I are two different
sets of timing charts alternatively used to drive the image-forming
apparatus of Example 9.
[0041] FIG. 25 is a block diagram of the display apparatus of
Example 10.
[0042] FIG. 26 is a schematic side view of an embodiment of step
type surface conduction electron-emitting device according to the
invention.
[0043] FIG. 27 is a schematic plan view of a conventional surface
conduction electron-emitting device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0044] Now, the present invention will be described in terms of
preferred embodiments of the invention.
[0045] The present invention relates to a novel surface conduction
electron-emitting device, a method of manufacturing the same and a
novel electron source incorporation such a device as well as an
image-forming apparatus such as a display apparatus incorporating
such an electron source and applications of such an apparatus.
[0046] A surface conduction electron-emitting device according to
the invention may be realized either as a flat type or as a step
type. Firstly, a flat type surface conduction electron-emitting
device will be described.
[0047] FIGS. 1A and 1B are schematic plan and sectional side views
showing the basic configuration of a flat type surface conduction
electron-emitting device according to the invention.
[0048] Referring to FIGS. 1A and 1B, the device comprises a
substrate 1, a pair of device electrodes 5 and 6, a thin film 4
including an electron-emitting region 3.
[0049] Materials that can be used for the substrate 1 include
quartz glass, glass containing impurities such as Na to a reduced
concentration level, soda lime glass, glass substrate realized by
forming an SiO.sub.2 layer on soda lime glass by means of
sputtering, ceramic substances such as alumina.
[0050] While the oppositely arranged device electrodes 5 and 6 may
be made of any highly conducting material, preferred candidate
materials include metals such as Ni, Cr, Au, Mo, W, Pt, Ti, Al, Cu
and Pd and their alloys, printable conducting materials made of a
metal or a metal oxide selected from Pd, Ag, RuO.sub.2, Pd--Ag and
glass, transparent conducting materials such as
In.sub.2O.sub.3--SnO.sub.2 and semiconductor materials such as
poly-silicon.
[0051] The distance L1 separating the device electrodes, the length
W1 of the device electrodes, the contour of the electroconductive
film 4 and other factors for designing a surface conduction
electron-emitting device according to the invention may be
determined depending on the application of the device. If, for
instance, it is used for an image-forming apparatus such as a
television set, it may have to have dimensions corresponding to
those of each pixel that may be very small if the television set is
of a high definition type, although it is required to provide a
satisfactory emission current in order to ensure sufficient
brightness for the screen of the television set while meeting the
rigorous dimensional requirements.
[0052] The distance L1 separating the device electrodes 5 and 6 is
preferably between hundreds nanometers and hundreds Micrometers
and, still preferably, between several micrometers and tens of
several micrometers depending on the voltage to be applied to the
device electrodes and the field strength available for electron
emission.
[0053] The length W1 of the device electrodes 5 and 6 is preferably
between several micrometers and hundreds of several micrometers
depending on tne resistance of the electrodes and the
electron-emitting characteristics of the device. The film thickness
d of the device electrodes 5 and 6 is between tens of several
nanometers and several micrometers.
[0054] A surface conduction electron-emitting device according to
the invention may have a configuration other than the one
illustrated in FIGS. 1A and 1B and, alternatively, it may be
prepared by laying a thin film 4 including an electron-emitting
region on a substrate 1 and then a pair of oppositely disposed
device electrodes 5 and 6 on the thin film.
[0055] The electroconductive thin film 4 is preferably a fine
particle film in order to provide excellent electron-emitting
characteristics. The thickness of the electroconductive thin film 4
is determined as a function of the stepped coverage of the thin
film on the device electrodes 5 and 6, the electric resistance
between the device electrodes 5 and 6 and the parameters for the
forming operation that will be described later as well as other
factors and preferably between a nanometer and hundreds of several
nanometers and more preferably between a nanometer and fifty
nanometers. The thin film 4 normally shows a resistance per unit
surface area between 10.sup.3 and 10.sup.7.OMEGA./.quadrature..
[0056] The thin film 4 including the electron-emitting region is
made of fine particles of a material selected from metals such as
Pd, Ru, Ag, Au, Ti, In, Cu, Cr, Fe, Zn, Sn, Ta, W and Pb, oxides
such as PdO, SnO.sub.2, In.sub.2O.sub.3, PbO and Sb.sub.2O.sub.3,
borides such as HfB.sub.2, ZrB.sub.2, LaB.sub.6, CeB.sub.6,
YB.sub.4 and GdB.sub.4, carbides such as TiC, ZrC, HfC, TaC, SiC
and WC, nitrides such as TiN, ZrN and HfN, semiconductors such as
Si and Ge and carbon.
[0057] The term "a fine particle film" as used herein refers to a
thin film constituted of a large number of fine particles that may
be loosely dispersed, tightly arranged or mutually and randomly
overlapping (to form an island structure under certain
conditions).
[0058] The diameter of fine particles to be used for the purpose of
the present invention is between a nanometer and hundreds of
several nanometers and preferably between a nanometer and twenty
nanometers.
[0059] The electron-emitting region is part of the
electroconductive thin film 4 and comprises electrically highly
resistive fissures, although it is dependent on the thickness and
the material of the electroconductive thin film 4 and the electric
forming process which will be described hereinafter. It may contain
electrocondcutive fine particles having a diameter between several
angstroms and hundreds of several angstroms. The material of the
electron-emitting region 3 may be selected from all or part of the
materials that can be used to prepare the thin film 4 including the
electron-emitting region. The thin film 4 contain carbon and/or
carbon compounds in the electron-emitting region 3 and its
neighboring areas.
[0060] A surface conduction type electron-emitting device according
to the invention and having an alternative profile, or a step type
surface conduction electron-emitting device, will be described.
[0061] FIG. 26 is a schematic perspective view of a step type
surface conduction electron-emitting device, showing its basic
configuration.
[0062] As seen in FIG. 26, the device comprises a substrate 1, a
pair of device electrodes 265 and 266 and a thin film 264 including
an electron-emitting region 263, which are made of materials same
as a flat type surface conduction electron-emitting device as
described above, as well as a step-forming section 261 made of an
insulating material such as SiO.sub.2 produced by vacuum
deposition, printing or sputtering and having a film thickness
corresponding to the distance L1 separating the device electrodes
of a flat type surface conduction electron-emitting device as
described above, or between tens of several nanometers and tens of
several micrometers and preferably between tens of several
nanometers and several micrometers, although it is selected as a
function of the method of producing the step-forming section used
there, the voltage to be applied to the device electrodes and the
field strength available for electron emission.
[0063] As the thin film 264 including the electron-emitting region
is formed after the device electrodes 265 and 266 and the
step-forming section 261, it may preferably be laid on the device
electrodes 265 and 266. While the electron-emitting region 263 is
shown to have straight outlines in FIG. 26, its location and
contour are dependent on the conditions under which it is prepared,
electric forming conditions and other related conditions and not
limited to straight outlines.
[0064] While various methods may be conceivable for manufacturing
an electron-emitting device including an electron-emitting region
3, FIGS. 2A through 2C illustrate a typical one of such
methods.
[0065] Now, a method of manufacturing a flat type surface
conduction electron-emitting device according to the invention will
be described by referring to FIGS. 1A and 1B and 2A through 2C.
[0066] 1) After thoroughly cleansing a substrate 1 with detergent
and pure water, a material is deposited on the substrate 1 by means
of vacuum deposition, sputtering or some other appropriate
technique for a pair of device electrodes 5 and 6, which are then
produced by photolithography (FIG. 2A).
[0067] 2) An organic metal thin film is formed on the substrate 1
between the pair of device electrodes 5 and 6 by applying an
organic metal solution and leaving the applied solution for a given
period of time. An organic metal solution as used herein refers to
a solution of an organic compound containing as a principal
ingredient a metal selected from the group of metals cited above
including Pd, Ru, Ag, Au, Ti, In, Cu, Cr, Fe, Zn, Sn, Ta, W and Pb.
Thereafter, the organic metal thin film is heated, sintered and
subsequently subjected to a patterning operation, using an
appropriate technique such as lift-off or etching, to produce a
thin film 2 for forming an electron-emitting region (FIG. 2B).
While an organic metal solution is used to produce a thin film in
the above description, a thin film may alternatively be formed by
vacuum deposition, sputtering, chemical vapor phase deposition,
dispersed application, dipping, spinner or some other
technique.
[0068] 3) Thereafter, the device electrodes 5 and 6 are subjected
to an electrically energizing process referred to as "forming",
where a pulse voltage or a rising voltage is applied to the device
electrodes 5 and 6 from a power source (not shown) to produce an
electron-emitting region 3 in the thin film 2 forming an
electron-emitting region (FIG. 2C). The area of the thin film 2 for
forming an electron-emitting region that has been locally
destroyed, deformed or transformed to undergo a structural change
is referred to as an electron-emitting region 3.
[0069] All the remaining steps of the electric processing including
the forming operation and the activation operation to be conducted
on the device are carried out by using a gauging system which will
be described below by referring to FIG. 3.
[0070] FIG. 3 is a schematic block diagram of a gauging system for
determining the performance of an electron-emitting device having a
configuration as illustrated in FIGS. 1A and 1B. In FIG. 3, the
device comprises a substrate 1, a pair of device electrodes 5 and
6, a thin film 4 including an electron-emitting region 3.
Otherwise, the gauging system comprises an ammeter 30 for metering
the device current If running through the thin film 4 including the
electron-emitting region 3 between the device electrodes 5 and 6, a
power source 31 for applying a device voltage Vf to the device, an
anode 34 for capturing the emission current Ie emitted from the
electron-emitting region of the device, a high voltage source 33
for applying a voltage to the anode 34 of the gauging system and
another ammeter 32 for metering the emission current Ie emitted
from the electron-emitting region 3 of the device.
[0071] For measuring the device current If and the emission current
Ie, the device electrodes 5 and 6 are connected to the power source
31 and the ammeter 30 and the anode 34 is placed above the device
and connected to the power source 33 by way of the ammeter 32. The
electron-emitting device to be tested and the anode 34 are put into
a vacuum chamber, which is provided with an exhaust pump, a vacuum
gauge and other pieces of equipment necessary to operate a vacuum
chamber so that the metering operation can be conducted under a
desired vacuum condition. The exhaust pump may be provided with an
ordinary high vacuum system comprising a turbo pump or a rotary
pump or an oil-free high vacuum system comprising an oil-free pump
such as a magnetic levitation turbo pump or a dry pump and an
ultra-high vacuum system comprising an ion pump.
[0072] The vacuum chamber of the gauging system is connected to an
ampoule or a gas bomb containing one or more than one organic
substances by way of a needle valve so that the operation of
activation may be carried out in the vacuum chamber, feeding the
organic substances in gaseous form into the vacuum chamber. The
feed rate may be regulated by controlling the needle valve and the
exhaust pump, monitoring the degree of vacuum in the chamber by
means of a vacuum gauge.
[0073] The vacuum chamber and the substrate of the electron source
can be heated to approximately 200.degree. C. by means of a heater
(not shown).
[0074] For determining the performance of the device, a voltage
between 1 and 10 KV is applied to the anode, which is spaced apart
from the electron-emitting device by distance H which is between 2
and 8 mm.
[0075] For the forming operation, a constant pulse voltage or a
increasing pulse voltage may be applied. The operation of using a
constant pulse voltage will be described first by referring to FIG.
4A, showing a pulse voltage having a constant pulse height.
[0076] In FIG. 4A, the pulse voltage has a pulse width T1 and a
pulse interval T2, which are between 1 and 10 microseconds and
between 10 and 100 milliseconds respectively. The height of the
triangular wave (the peak voltage for the electric forming
operation) may be appropriately selected so long as the voltage is
applied in vacuum.
[0077] FIG. 4B shows a pulse voltage whose pulse height increases
with time. In FIG. 4B, the pulse voltage has an width T1 and a
pulse interval T2, which are between 1 and 10 microseconds and
between 10 and 100 milliseconds respectively. The height of the
triangular wave (the peak voltage for the electric forming
operation) is increased at a rate of, for instance, 0.1 V per step
in vacuum.
[0078] The electric forming operation will be terminated when
typically a resistance greater than 1 M ohms is observed for the
device current running through the thin film 2 for forming an
electron-emitting region while applying a voltage of approximately
0.1 V is applied to the device electrodes to locally destroy or
deform the thin film. The voltage observed when the electric
forming operation is terminated is referred to as the forming
voltage Vf.
[0079] While a triangular pulse voltage is applied to the device
electrodes to form an electron-emitting region in an electric
forming operation as described above, the pulse voltage may have a
different wave form such as rectangular form and the pulse width
and the pulse interval may be of values other than those cited
above so long as they are selected as a function of the device
resistance and other values that meet the requirements for forming
an electron-emitting region. Additionally, since the forming
voltage is unequivocally defined in terms of the material and the
configuration of the device and other related factors, it is
preferable to apply a pulse voltage having an increasing wave
height rather than to apply a pulse voltage with a constant wave
height because a desired energy level may be easily selected for
each device to give rise to desired electron emission
characteristics for the device.
[0080] 4) After the electric forming operation, the device is
subjected to an activation process, where a pulse voltage having a
constant wave height is repeatedly applied to the device in vacuum
of a desired degree as in the case of the forming operation so that
carbon and/or carbon compounds may be deposited on the device out
of the organic substances existing in the vacuum in order to cause
the device current If and the emission current Ie of the device to
change markedly (hereinafter referred to as activation process).
Organic substances can be supplied into vacuum by arranging in the
turbo pump or the rotary pump containing the organic substances in
such a way that the organic substances are also held in vacuum or,
preferably, by feeding one or more than one predetermined carbon
compounds into the vacuum chamber containing the device but not any
oil. Carbon compounds to be fed into the vacuum chamber are
preferably organic substances. The activation process is terminated
when the emission current Ie gets to a saturation point while
gauging the device current If and the emission current Ie. FIG. 5
typically shows how the device current If and the emission current
Ie are dependent on the duration of the activation process. It
should also be noted that, in the activation process, the time
dependency of the device current If and the emission current Ie
varies as a function of the degree of vacuum and the pulse voltage
applied to the device and that the contour and the state of the
deformed or transformed portion of the thin film depend on how the
forming process is carried out. In FIG. 5, the time dependency of
the device current If and the emission current Ie is illustrated
for a typical high resistance activation process and a typical low
resistance activation process. In either case, it will be seen that
the emission current Ie increases with the duration of the
activation process so that the device may eventually reach a level
of emission current Ie required for its application.
[0081] Organic substances that can suitably be used for the purpose
of the invention show a vapor pressure greater 0.2 hPa and smaller
than 5,000 hPa and preferably greater than 10 hPa and smaller than
5,000 hPa at temperature where they are effectively adsorbed by the
area 3 of the device that has been deformed or transformed in the
forming process.
[0082] The activation process is preferably conducted at room
temperature from the viewpoint of feeding organic substances and
controlling the temperature of the device.
[0083] If the activation process is conducted at 20.degree. C.,
organic substances that can suitably be used for the purpose of the
invention needs to show a vapor pressure greater than 0.2 hPa and
smaller than 5,000 hPa.
[0084] Organic substances that can be used for the purpose of the
invention include aliphatic hydrocarbons such as alkanes, alkenes
and alkynes, aromatic hydrocarbons, alcohols, aldehydes, ketones,
amines and organic acids such as phenylic acids, carbonic acids and
sulfonic acids as well as their derivatives that may produce a
required vapor pressure.
[0085] Some specific organic substances to be suitably used for the
purpose of the invention includes butadiene, n-hexane, 1-hexane,
benzene, toluene, oxylene, benzonitrile, chloroethylene,
trichloroethylene, methanol, ethanol, isopropyl alcohol,
formaldehyde, acetaldehyde, propanol, acetone, ethyl methyl ketone,
diethyl ketone, methyl amine, ethyl amine, ethylene diamine,
phenol, formic acid, acetic acid and propionic acid.
[0086] The activation process may become excessively time consuming
and not practical for an electron-emitting device according to the
invention, if the vapor pressure of organic substances exceeds
5,000 hPa at 20.degree. C. in the vacuum chamber.
[0087] If, on the other hand, the vapor pressure of organic
substances in the vacuum chamber falls under 0.2 hPa at 20.degree.
C. in the vacuum chamber, the operation of depositing additional
carbon and/or carbon compounds in Step 5) described below becomes
impracticable and the device current If and the emission current Ie
may have difficulty to get to a constant level. If such is the
case, the emission current may become variable as the pulse width
of the drive voltage for driving the device changes (a phenomenon
to be referred to pulse width dependency hereinafter). This
phenomenon may be attributable to the adsorption residue of the
organic substances such as ingredients of oil left on an area in
and near the electron-emitting region of the device that becomes
hardly removable after the activation process. Once such a
phenomenon becomes existent, so-called pulse modulation or the
technique of controlling the rate of electron emission of an
electron-emitting device by controlling the pulse width of the
pulse voltage applied to the device and hence gradated display of
images on a display medium comprising electron-emitting devices
arranged in the form of simple matrix (as will described
hereinafter) will not be feasible any longer.
[0088] If, additionally, a large number of electron-emitting
devices are arranged in a narrow space as in the case of a flat
type display panel as will be described hereinafter, highly
adsorbable organic substances such as ingredients of oil to be used
for activation can hardly be distributed evenly within the narrow
space nor removed after the activation process so that the
pulse-width dependency of the devices may be adversely
affected.
[0089] For the above described reasons, the vapor pressure of the
organic substances in the activation process is preferably between
0.2 hPa and 5,000 hPa at 20.degree. C.
[0090] The feeding partial pressure of the organic substances is
preferably between 10.sup.-2 and 10.sup.-7 torr when an ordinary
exhaust device is used.
[0091] Assuming that the vapor pressure of the crganic substances
is PrO and the feeding partial pressure is Pr, the feeding partial
pressure Pr is preferably greater than PrO.times.10.sup.-8 and
determined as a function of the organic substances involved.
[0092] If the feeding partial pressure of the organic substances is
lower than the above level, the activation process may become
excessively time consuming and not practical for an
electron-emitting device according to the invention.
[0093] The activation process is referred to as a high resistance
activation process when the pulse voltage used in the process is
sufficiently high relative to the forming voltage Vform, whereas it
is referred to as a low resistance activation process when the
pulse voltage used in the process is sufficiently low relative to
the forming voltage Vform. More specifically, the initial voltage
Vp that indicates the voltage controlled negative resistance of the
device as defined hereinafter provides a reference for the above
distinction. Note that electron-emitting devices activated by a
high resistance activation process are preferable than those
activated by a low resistance activation process from the viewpoint
of performance. More specifically, the activation process is
preferably conducted on an electron-emitting device according to
the invention with the operating voltage of the device.
[0094] FIGS. 6A and 6B schematically illustrate how an
electron-emitting device according to the invention is treated in
the high and low resistance activation processes when observed
through an FESEM or TEM. FIGS. 6A and 6B respectively show
schematic cross sectional views of a device treated by a high
resistance activation process and a low resistance activation
process. In a high resistance activation process (FIG. 6A), carbon
and/or carbon compounds are remarkably deposited on the high
potential side of the device partly beyond the area 3 deformed or
transformed by electric forming, whereas they are only slightly
deposited on the low potential side of the device. When observed
through a microscope having large magnifying power, a deposit of
carbon and/or carbon compounds is found on and near some of the
fine particles of the device and, in some cases, even on the device
electrodes if the electrodes are located relatively close to each
other. The thickness of the film deposit is preferably less than
500 angstroms and more preferably less than 3,000 angstroms.
[0095] When observed through a TEM or Roman microscope, it is found
that the deposited carbon and/or carbon compounds are mostly
graphite (both mono- and polycrystalline) and non-crystalline
carbon (or a mixture of non-crystalline carbon and poly-crystalline
graphite).
[0096] In a low resistance activation process (FIG. 6B), on the
other hand, a deposit of carbon and/or carbon compounds is found
only in the area 3 that has been deformed or transformed by
electric forming. When observed through a microscope having large
magnifying power, a deposit of carbon and/or carbon compounds is
also found on and near some of the fine particles of the
device.
[0097] FIG. 5 shows that a low resistance activation process makes
both the device and emission currents of a device according to the
invention higher than a high resistance activation process.
[0098] 5) An electron-emitting device that has been treated in an
electric forming process and an activation process is then driven
to operate in a vacuum of a degree higher than that of the
activation process. Here, a vacuum of a degree higher than that of
the activation process means a vacuum of a degree greater than
10.sup.-6 and, preferably, an ultra-high vacuum where no carbon nor
carbon compounds cannot be additionally deposited on the
device.
[0099] Thus, no carbon nor carbon compounds would be deposited
thereafter to establish stable device and emission currents If and
Ie.
[0100] Now, some of the basic features of an electron-emitting
device according to the invention and prepared in the above
described manner will be described below by referring to FIG.
7.
[0101] FIG. 7 shows a graph schematically illustrating the
relationship between the device voltage Vf and the emission current
Ie and the device current If typically observed by the gauging
system of FIG. 3. Note that different units are arbitrarily
selected for Ie and If in FIG. 7 in view of the fact that Ie has a
magnitude by far smaller than that of If. As seen in FIG. 7, an
electron-emitting device according to the invention has three
remarkable features in terms of emission current Ie, which will be
described below.
[0102] Firstly, an electron-emitting device according to the
invention shows a sudden and sharp increase in the emission current
Ie when the voltage applied thereto exceeds a certain level (which
is referred to as a threshold voltage hereinafter and indicated by
Vth in FIG. 7), whereas the emission current Ie is practically
undetectable when the applied voltage is found lower than the
threshold value Vth. Differently stated, an electron-emitting
device according to the invention is a non-linear device having a
clear threshold voltage Vth to the emission current Ie.
[0103] Secondly, since the emission current Ie is highly dependent
on the device voltage Vf, the former can be effectively controlled
by way of the latter.
[0104] Thirdly, the emitted electric charge captured by the anode
34 is a function of the duration of time of application of the
device voltage Vf. In other words, the amount of electric charge
captured by the anode 34 can be effectively controlled by way of
the time during which the device voltage Vf is applied.
[0105] Because of the above remarkable features, it will be
understood that the electron-emitting behavior of an electron
source comprising a plurality of electron-emitting devices
according to the invention and hence that of an image-forming
apparatus incorporating such an electron source can easily be
controlled in response to the input signal. Thus, such an electron
source and an image-forming apparatus may find a variety of
applications.
[0106] On the other hand, the device current If either
monotonically increases relative to the device voltage Vf (as shown
by a solid line in FIG. 7, a characteristic referred to as MI
characteristic hereinafter) or changes to show a form specific to a
voltage-controlled-negative-resistan- ce characteristic (as shown
by a broken line in FIG. 5, a characteristic referred to as VCNR
characteristic hereinafter). These characteristics of the device
current are dependent on a number of factors including the
manufacturing method, the conditions where it is gauged and the
environment for operating the device. The critical voltage for the
VCNR characteristic to become apparent is referred to as the
boundary voltage VP.
[0107] Thus, it has been discovered that the VCNR characteristic of
the device current If varies remarkably as a function of a number
of factors including the electric conditions of the electric
forming process, the vacuum conditions of the vacuum system, the
vacuum and electric conditions of the gauging system particularly
when the performance of the electron-emitting device is gauged in
the vacuum gauging system after the electric forming process (e.g.,
the sweep rate at which the voltage being applied to the
electron-emitting device is swept from low to high in order to
determine the current-voltage characteristic of the device) and the
duration of time for the electron-emitting device to have been left
in the vacuum system before the gauging operation, although the
device current of the electron-emitting device never loses the
above identified three features.
[0108] Now, an electron source according to the invention will be
described.
[0109] An electron source and hence an image-forming apparatus can
be realized by arranging a plurality of electron-emitting devices
according to the invention on a substrate. Electron-emitting
devices may be arranged on a substrate in a number of different
modes. For instance, a number of surface conduction
electron-emitting devices as described earlier by referring to a
light source may be arranged in rows along a direction (hereinafter
referred to row-direction), each device being connected by wirings
at opposite ends thereof, and driven to operate by control
electrodes (hereinafter referred to as grids or modulation means)
arranged in a space above the electron-emitting devices along a
direction perpendicular to the row direction (hereinafter referred
to as column-direction), or, alternatively as described below, a
total of m X-directional wiring and a total of n Y-directional
wirings are arranged with an interlayer insulation layer disposed
between the X-directional wirings and the Y-directional wiring
along with a number of surface conduction electron-emitting devices
such that the pair of device electrodes of each surface conduction
electron-emitting device are connected respectively to one of the
X-directional wiring and one of the Y-directional wirings. The
latter arrangement is referred to as a simple matrix arrangement.
Now, the simple matrix arrangement will be described in detail.
[0110] In view of the three basic features of a surface conduction
electron-emitting device according to the invention, each of the
surface conduction electron-emitting devices having a simple matrix
arrangement configuration can be controlled for electron emission
by controlling the wave height and the pulse width of the pulse
voltage applied to the opposite electrodes of the device above the
threshold voltage level. On the other hand, the device does not
emit any electrons below the threshold voltage level. Therefore,
regardless of the number of electron-emitting devices, desired
surface conduction electron-emitting devices can be selected and
controlled for electron emission in response to the input signal by
applying a pulse voltage to each of the selected devices.
[0111] FIG. 8 is a schematic plan view of the substrate of an
electron source according to the invention ealized by using the
above feature. In FIG. 8, the electron source comprises a substrate
81, X-directional wirings 82, Y-directional wirings 83, surface
conduction electron-emitting devices 84 and connecting wires 85.
The surface conduction electron-emitting devices may be either of
the flat type or of the step type.
[0112] In FIG. 8, the substrate 81 of the electron source may be a
glass substrate and the number and configuration of the surface
conduction electron-emitting devices arranged on the substrate may
be appropriately determined depending on the application of the
electron source.
[0113] There are provided a total of m X-directional wirings 82,
which are donated by DX1, DX2, . . . , DXm and made of a conductive
metal formed by vacuum deposition, printing or sputtering. These
wirings are so designed in terms of material, thickness and width
that, if necessary, a substantially equal voltage may be applied to
the surface conduction electron-emitting devices. A total of n
Y-directional wirings are arranged and donated by DY1, DY2, . . . ,
DYn, which are similar to the X-directional wirings in terms of
material, thickness and width. An interlayer insulation layer (not
shown) is disposed between the m X-directional wirings and the n
Y-directional wirings to electrically isolate them from each other,
the m X-directional wirings and n Y-directional wirings forming a
matrix. (m and n are integers.)
[0114] The interlayer insulation layer (not shown) is typically
made of SiO.sub.2 and formed on the entire surface or part of the
surface of the insulating substrate 81 to show a desired contour by
means of vacuum deposition, printing or sputtering. The thickness,
material and manufacturing method of the interlayer insulation
layer are so selected as to make it withstand any potential
difference between an X-directional wiring 82 and a Y-directional
wiring 83 at the crossing thereof. Each of the X-directional
wirings 82 and the Y-directional wirings 83 is drawn out to form an
external terminal.
[0115] The oppositely arranged electrodes (not shown) of each of
the surface conduction electron-emitting devices 84 are connected
to the related one of the m X-directional wirings 82 and the
related one of the n Y-directional wirings 83 by respective
connecting wires 85 which are made of a conductive metal and formed
by vacuum deposition, printing or sputtering.
[0116] The electroconductive metal material of the device
electrodes and that of the connecting wires 85 extending from the m
X-directional wirings 82 and the n Y-directional wirings 83 may be
same or contain common elements as ingredients, the latter being
appropriately selected depending on the former. If the device
electrodes and the connecting wires are made of a same material,
they may be collectively called device electrodes without
discriminating the connecting wires. The surface conduction
electron-emitting devices may be arranged directly on the substrate
81 or on the interlayer insulation layer (not shown).
[0117] The X-directional wirings 82 are electrically connected to a
scan signal generating means (not shown) for applying a scan signal
to a selected row of surface conduction electron-emitting devices
84 and scanning the selected row according to an input signal.
[0118] On the other hand, the Y-directional wirings 83 are
electrically connected to a modulation signal generating means (not
shown) for applying a modulation signal to a selected column of
surface conduction electron-emitting devices 84 and modulating the
selected column according to an input signal.
[0119] Note that the drive signal to be applied to each surface
conduction electron-emitting device is expressed as the voltage
difference of the scan-signal and the modulation signal applied to
the device.
[0120] Now, an image-forming apparatus according to the invention
and comprising an electron source having a simple matrix
arrangement as described above will be described by referring to
FIG. 9 and FIGS. 10A and 10B. This apparatus may be a display
apparatus. Referring firstly to FIG. 9 illustrating the basic
configuration of the display panel of the image-forming apparatus,
it comprises an electron source substrate 81 of the above described
type, a rear plate 91 rigidly holding the electron source substrate
81, a face plate 96 produced by laying a fluorescent film 94 and a
metal back 95 on the inner surface of a glass substrate 93 and a
support frame 92. An enclosure 98 is formed for the apparatus as
frit glass is applied to said rear plate 91, said support frame 92
and said face plate 96, which are subsequently baked to 400 to
500.degree. C. in the atmosphere or in nitrogen and bonded
together.
[0121] In FIG. 9, reference numeral 84 denotes the
electron-emitting region of each electron-emitting device and
reference numerals 82 and 83 respectively denotes the X-directional
wiring and the Y-directional wiring connected to the respective
device electrodes of each electron-emitting device.
[0122] While the enclosure 98 is formed of the face plate 96, the
support frame 92 and the rear plate 91 in the above described
embodiment, the rear plate 91 may be omitted if the substrate 81 is
strong enough by itself. If such is the case, an independent rear
plate 91 may not be required and the substrate 81 may be directly
bonded to the support frame 92 so that the enclosure 98 is
constituted of a face plate 96, a support frame 92 and a substrate
81. The overall strength of the enclosure 98 may be increased by
arranging a number of support members called spacers (not shown)
between the face plate 96 and the rear plate 91.
[0123] FIGS. 10A and 10B schematically illustrate two possible
arrangements of fluorescent bodies to form a fluorescent film 94.
While the fluorescent film 94 comprises only fluorescent bodies if
the display panel is used for showing black and white pictures, it
needs to comprises for displaying color pictures black conductive
members 101 and fluorescent bodies 102, of which the former are
referred to as black stripes or members of a black matrix depending
on the arrangement of the fluorescent bodies. Black stripes or
members of a black matrix are arranged for a color display panel so
that the fluorescent bodies 102 of three different primary colors
are made less discriminable and the adverse effect of reducing the
contrast of displayed images of external light is weakened by
blackening the surrounding areas. While graphite is normally used
as a principal ingredient of the black stripes, other conductive
material having low light transmissivity and reflectivity may
alternatively be used.
[0124] A precipitation or printing technique is suitably be used
for applying a fluorescent material on the glass substrate
regardless of black and white or color display.
[0125] An ordinary metal back 95 is arranged on the inner surface
of the fluorescent film 94. The metal back 95 is provided in order
to enhance the luminance of the display panel by causing the rays
of light emitted from the fluorescent bodies and directed to the
inside of the enclosure to turn back toward the face plate 96, to
use it as an electrode for applying an accelerating voltage to
electron beams and to protect the fluorescent bodies against
damages that may be caused when negative ions generated inside the
enclosure collide with them. It is prepared by smoothing the inner
surface of the fluorescent film 94 (in an operation normally called
"filming") and forming an Al film thereon by vacuum deposition
after forming the fluorescent film 94.
[0126] A transparent electrode (not shown) may be formed on the
face plate 96 facing the outer surface of the fluorescent film 94
in order to raise the conductivity of the fluorescent film 94.
[0127] Care should be taken to accurately align each set of color
fluorescent bodies and an electron-emitting device, if a color
display is involved, before the above listed components of the
enclosure are bonded together.
[0128] The enclosure 98 is then evacuated by way of an exhaust pipe
(not shown) to a degree of vacuum of approximately 10.sup.-6 and
hermetically sealed.
[0129] After evacuating the enclosure to a desired degree of vacuum
by way of an exhaust pipe (not shown), a voltage is applied to the
device electrodes of each device by way of external terminals Dx1
through Dxm and Dy1 through Dyn for a forming operation and then
desired organic substances are fed in under a vacuum condition for
an activation process in order to produce an electron-emitting
region 3 of the device.
[0130] Most preferably, a baking operation is carried out at
80.degree. C. to 200.degree. C. for 3 to 15 hours, during which the
vacuum system in the enclosure is switched to an ultra-high vacuum
system comprising an ion pump or the like. The switch to an
ultra-high vacuum system and the baking operation are intended to
ensure the surface conduction electron-emitting device a
satisfactorily monotonically increasing characteristic (MI
characteristic) for both the device current If and the emission
current Ie and, therefore, this objective may be achieved by some
other means under different conditions. A getter operation may be
carried out after sealing the enclosure 98 in order to maintain
that degree of vacuum in it. A getter operation is an operation of
heating a getter (not shown) arranged at a given location in the
enclosure 98 immediately before of after sealing the enclosure 98
by resistance heating or high frequency heating to produce a vapor
deposition film. A getter normally contains Ba as a principle
ingredient and the formed vapor deposition film can typically
maintain the inside of the enclosure to a degree of
1.times.10.sup.-5 to 10.sup.-7 Torr by its adsorption effect.
[0131] An image-forming apparatus according to the invention and
having a configuration as described above is operated by applying a
voltage to each electron-emitting device by way of the external
terminal Dox1 through Doxm and Doy1 through Doyn to cause the
electron-emitting devices to emit electrons. Meanwhile, a high
voltage is applied to the metal back 85 or the transparent
electrode (not shown) by way of high voltage terminal Hv to
accelerate electron beams and cause them to collide with the
fluorescent film 94, which by turn is energized to emit light to
display intended images.
[0132] While the configuration of a display panel to be suitably
used for an image-forming apparatus according to the invention is
outlined above in terms of indispensable components thereof, the
materials of the components are not limited to those described
above and other materials may appropriately be used depending on
the application of the apparatus. Input signals for the above
image-forming apparatus is not limited to NTSC signals and signals
in other ordinary television systems such as PAL and SECAM and
those of television systems with a greater number of scanning lines
(such as MUSE and other high definition systems) may be made
compatible with the apparatus.
[0133] The basic ideal of the present invention may be utilized to
provide not only display apparatuses for television but also those
for television conferencing, computer systems and other
applications. Additionally, an image-forming apparatus to be used
for an optical printer comprising a photosensitive drum may be
realized on the basis of the present invention.
EXAMPLES
[0134] Now, the present invention will be described in greater
detail by way of examples.
Example 1
[0135] Device specimens used in this example had a basic
configuration same as the one illustrated in the plan view of FIG.
1A and the sectional view of FIG. 1B. Four identical devices were
formed on a substrate 1. Note that the reference numeral in FIG. 11
denote respective components identical with those of FIGS. 1A and
1B.
[0136] The method of manufacturing the devices was basically same
as the one illustrated in FIGS. 2A through 2C. The basic
configuration of the device specimen and the method for
manufacturing the same will be described below by referring to
FIGS. 1A and 1B and FIGS. 2A through 2C.
[0137] Referring to FIGS. 1A and 1B, the prepared specimens of
electron-emitting device comprised a substrate 1, a pair of device
electrodes 5 and 6, a thin film 4 including an electron-emitting
region 3.
[0138] The method used for manufacturing the devices will be
described below in terms of an experiment conducted for the
specimens, referring to FIGS. 1A and 1B and FIGS. 2A through
2C.
[0139] Step A
[0140] After thoroughly cleansing a soda lime glass plate a silicon
oxide film was formed thereon to a thickness of 0.5 microns by
sputtering to produce a substrate 1, on which a pattern of
photoresist (RD-2000N-41: available from Hitachi Chemical Co.,
Ltd.) was formed for a pair of device electrodes 5 and 6 and a gap
G separating the electrodes and then Ti and Ni were sequentially
deposited thereon respectively to thicknesses of 50 A and 1,000 A
by vacuum deposition. The photoresist pattern was dissolved by an
organic solvent and the Ni/Ti deposit film was treated by using a
lift-off technique to produce a pair of device electrodes 5 and 6
having a width W1 of 300 microns and separated from each other by a
distance L1 of 3 microns.
[0141] Step B
[0142] A Cr film was formed to a film thickness of 1,000 A by
vacuum deposition, which was then subjected to a patterning
operation. Thereafter, organic Pd (ccp4230: available from Okuno
Pharmaceutical Co., Ltd.) was applied to the Cr film by means of a
spinner, while rotating the film, and baked at 300.degree. C. for
10 minutes to produce a thin film 2 for forming an
electron-emitting region, which was made of fine particles
containing Pd as a principal ingredient and had a film thickness of
100 angstroms and an electric resistance per unit area of
2.times.10.sup.4.OMEGA./.quadrature.. Note that the term "a fine
particle film" as used herein refers to a thin film constituted of
a large number of fine particles that may be loosely dispersed,
tightly arranged or mutually and randomly overlapping (to form an
island structure under certain conditions). The diameter of fine
particles to be used for the purpose of the present invention is
that of recognizable fine particles arranged in any of the above
described states.
[0143] Step C
[0144] The Cr film and the baked thin film 2 for forming an
electron-emitting region were etched by using an acidic etchant to
produce a desired pattern.
[0145] Now, a pair of device electrodes 5 and 6 and a thin film 2
for forming an electron-emitting region were produced on the
substrate 1.
[0146] Step D
[0147] Then, a gauging system as illustrated in FIG. 3 was set in
position and the inside was evacuated by means of an exhaust pump
to a degree of vacuum of 2.times.10.sup.-5 torr. Subsequently, a
voltage was applied to the device electrodes 5, 6 for electrically
energizing the device (electric forming process) by the power
source 31 provided there for applying a device voltage Vf to the
device. FIG. 4B shows the waveform of the voltage used for the
electric forming process.
[0148] In FIG. 4B, T1 and T2 respectively denote the pulse width
and the pulse interval of the applied pulse voltage, which were
respectively 1 millisecond and 10 milliseconds for the experiment.
The wave height (the peak voltage for the forming operation) of the
applied pulse voltage was increased stepwise with a step of 0.1 V.
During the forming operation, a resistance measuring pulse voltage
of 0.1 V was inserted during each T2 to determine the current
resistance of the device. The forming operation was terminated when
the gauge for the resistance measuring pulse voltages showed a
reading of resistance of approximately 1 M ohms. In the experiment,
the reading of the gauge for the forming voltage Vform was 5.1 V,
5.0 V, 5.0 V and 5.15 V.
[0149] Step E
[0150] Two pairs of devices that had undergone a forming process
were subjected to an activation process, where voltages having a
rectangular waveform (FIG. 4C) with wave heights of 4 V and 14 V
were respectively applied to each pair of devices. Hereinafter, the
specimens subjected to a low resistance activation process with 4 V
will be referred to as devices A, whereas the specimens subjected
to a high resistance activation process with 14 V will be referred
to as devices B. In the activation process, the above described
pulse voltages were applied to the device electrodes of the
respective devices in the gauging system of FIG. 3, while observing
the device current If and the emission current Ie. The degree of
vacuum in the gauging system of FIG. 3 was 1.5.times.10.sup.-5
torr. The activation process continued for 30 minutes for each
device.
[0151] An electron-emitting region 3 was then formed on each of the
devices to produce a complete electron-emitting device.
[0152] In an attempt to see the properties and the profile of the
surface conduction electron-emitting devices prepared through the
preceding steps, a device A and a device B were observed for
electron-emitting performance, using a gauging system as
illustrated in FIG. 3. The remaining pair of devices were observed
through a microscope.
[0153] In the above observation, the distance between the anode and
the electron-emitting device was 4 mm and the potential of the
anode was 1 kV, while the degree of vacuum in the vacuum chamber of
the system was held to 1.times.10.sup.-6 torr throughput the
gauging operation. A device voltage of 14 V was applied between the
device electrodes 5, 6 of each of the devices A and B to see the
device current If and the emission current Ie under that condition.
A device current If of approximately 10 mA began to flow through
the device A immediately after the start of measurement but the
current gradually declined and the emission current Ie also showed
a decline. On the other hand, a steady flow was observed for both
the device current If and the emission current Ie in the device B
from the start of measurement. A device current If of 2.0 mA and an
emission current Ie of 1.0 .mu.A were observed for a device voltage
of 14 V to provides an electron emission efficiency
.theta.=Ie/If(%) of 0.05%. Thus, it will be seen that the device A
showed a large and unstable device current If in the initial stages
of measurement whereas the device B proved to be stable and have an
excellent electron emission efficiency .theta. from the very start
of measurement.
[0154] When the degree of vacuum in the activation process was held
to be 1.5.times.10.sup.-5 torr for a device B and the device
current If and the emission current Ie were observed, sweeping the
device with a triangular pulse voltage with a frequency of
approximately 0.005 Hz, the device current If was such as indicated
by the broken line in FIG. 7. As seen from FIG. 7, the device
current If monotonically increased to approximately 5 V and then
showed a voltage-controlled-negative-resistanc- e above the 5 V
level. The device voltage at which the device current If reaches a
peak is referred to VP, which was 5 V for the specimen. It should
be noted that the device current If was reduced to a fraction of
the maximum device current or approximately 1 mA beyond 10 V.
[0155] When observed through a microscope, the devices A and B
showed profiles similar to those illustrated in FIGS. 6B and 6A
respectively. From a comparison between FIG. 6B and FIG. 6A, it was
found that the device A carried a coat formed in the area of the
thin film between the device electrodes that had been transformed,
while in case of the device B, a coat was formed mainly on the high
potential side from part of the transformed area along the
direction along which a voltage was applied to the device in the
activation process. When observed through an FESEM having large
magnifying power, it was found that the coat existed around part of
the fine metal particles and in part of the inter-particle space of
the device.
[0156] When observed through a TEM or a Raman microscope, it was
found that the coat was made of graphite and amorphous carbon.
[0157] From these observations, it may be safe to say that carbon
was produced in the area of the thin film of the device A that had
been transformed by the forming process as the area was activated
by a voltage below the voltage level of Vp required for
voltage-controlled-negative-re- sistance as described above so that
the carbon coat formed between the high and low potential sides of
the transformed area of the thin film provided a current path for
the device current through which a large device current was allowed
to flow at a rate several times greater than the device current of
the device B from the very beginning.
[0158] Contrary to this, the device B was activated by a voltage
above the voltage level of Vp required for
voltage-controlled-negative-resistance in a high resistance
activation process so that, if a carbon coat had been formed, it
may have been electrically disrupted to ensure a stable device
current to flow fro the beginning.
[0159] Thus, an electron-emitting device having a device current If
and a emission current Ie that are stable and capable of
efficiently emitting electron can be prepared by a high resistance
activation process.
Example 2
[0160] In this example, a large number of surface conduction
electron-emitting devices were arranged to a simple matrix
arrangement to produce an image-forming apparatus.
[0161] FIG. 13 is an enlarged schematic partial plan view of the
substrate of the electron source of the apparatus. FIG. 14 is an
enlarged schematic sectional side view of the substrate of FIG. 13
taken along line A-A'. Note that reference symbols in FIGS. 13, 14,
15A through 15D and 16E through 16H respectively denote identical
items throughout the drawings. Thus, reference numerals 81, 82 and
83 respectively denote a substrate, an X-directional wiring
corresponding. to an external terminal Dxm (also referred to as a
lower wiring) and a Y-direction wiring corresponding to an external
terminal Dyn (also referred to as an upper wiring), whereas
reference numeral 4 denotes a thin film including an
electron-emitting region, reference numerals 5 and 6 denote a pair
of device electrodes and reference numerals 141 and 142
respectively denotes an interlayer insulation layer and a contact
hole for connecting a device electrode 5 and a lower wiring 82.
[0162] Now, the method of manufacturing the device specimens will
be described below in terms of an experiment conducted for the
apparatus, referring to FIGS. 15A through 15D and 16E through
16H.
[0163] Step A
[0164] After thoroughly cleansing a soda lime glass plate a silicon
oxide film was formed thereon to a thickness of 0.5 microns by
sputtering to produce a substrate 81, on which a photoresist
(AZ1370: available from Hoechst Corporation) was formed by means of
a spinner, while rotating the film, and baked. Thereafter, a
photo-mask image was exposed to light and developed to produce a
resist pattern for the lower wirings 82 and then the deposited
Au/Cu film was wet-etched to produce lower wires 82 having a
desired profile (FIG. 15A).
[0165] Step B
[0166] A silicon oxide film was formed as an interlayer insulation
layer 141 to a thickness of 1.0 micron by RF sputtering (FIG.
15B).
[0167] Step C
[0168] A photoresist pattern was prepared for producing a contact
hole 142 in the silicon oxide film deposited in Step B, which
contact hole 142 was then actually formed by etching the interlayer
insulation layer, using the photoresist pattern for a mask. RIE
(Reactive Ion Etching) using CF.sub.4 and H.sub.2 gas was employed
for the etching operation (FIG. 15C).
[0169] Step D
[0170] Thereafter, a pattern of photoresist (RD-2000N: available
from Hitach Chemical Co., Ltd.) was formed for a pair of device
electrodes 5 and 6 and a gap G separating the electrodes and then
Ti and Ni were sequentially deposited thereon respectively to
thicknesses of 50 A and 1,000 A by vacuum deposition. The
photoresist pattern was dissolved by an organic solvent and the
Ni/Ti deposit film was treated by using a lift-off technique to
produce a pair of device electrodes 5 and 6 having a width W1 of
300 microns and separated from each other by a distance G of 3
microns (FIG. 15D).
[0171] Step E
[0172] After forming a photoresist pattern on the device electrodes
5, 6 for upper wirings 83, Ti and Au were sequentially deposited by
vacuum deposition to respective thicknesses of 5 nm and 500 nm and
then unnecessary areas were removed by means of the lift-off
technique to produce upper wirings 83 having a desired profile
(FIG. 16E).
[0173] Step F
[0174] A mask of the thin film 2 was prepared for forming the
electron-emitting region of the device. The mask had an opening for
the gap L1 separating the device electrodes and its vicinity. The
mask was used to form a Cr film 151 to a film thickness of 1,000 A
by vacuum deposition, which was then subjected to a patterning
operation. Thereafter, organic Pd (ccp4230: available from Okuno
Pharmaceutical Co., Ltd.) was applied to the Cr film by means of a
spinner, while rotating the film, and baked at 300.degree. C. for
10 minutes to produce a thin film 2 for forming an
electron-emitting region, which was made of fine particles
containing Pd as a principal ingredient and had a film thickness of
8.5 nm and an electric resistance per unit area of
3.9.times.10.OMEGA./.quadrature.. Note that the term "a fine
particle film" as used herein refers to a thin film constituted of
a large number of fine particles that may be loosely dispersed,
tightly arranged or mutually and randomly overlapping (to form an
island structure under certain conditions). The diameter of fine
particles to be used for the purpose of the present invention is
that of recognizable fine particles arranged in any of the above
described states (FIG. 16F).
[0175] Step G
[0176] The Cr film 151 and the baked thin film 2 for forming an
electron-emitting region were etched by using an acidic etchant to
produce a desired pattern (FIG. 16G).
[0177] Step H
[0178] Then, a pattern for applying photoresist to the entire
surface area except the contact hole 142 was prepared and Ti and Au
were sequentially deposited by vacuum deposition to respective
thicknesses of 5 nm and 500 nm. Any unnecessary areas were removed
by means of the lift-off technique to consequently bury the contact
hole 142.
[0179] Now, a lower wirings 82, an interlayer insulation layer 141,
upper wirings 83, a pair of device electrodes 5 and 6 and a thin
film 2 for forming an electron-emitting region were produced on the
substrate 81 (FIG. 16H).
[0180] In an experiment, an image-forming apparatus was produced by
using an electron source prepared in the above experiment. This
apparatus will be described by referring to FIGS. 8 and 9.
[0181] A substrate 81 carrying thereon a large number of surface
conduction electron-emitting devices prepared according to the
above described process was rigidly fitted to a rear plate 91 and
thereafter a face plate (prepared by forming a fluorescent film 94
and a metal back 95 on a glass substrate 93) was arranged 5 mm
above the substrate 81 by interposing a support frame 92
therebetween. Frit glass was applied to junction areas of the face
plate 96, the support frame 92 and the rear plate 91, which were
then baked at 400.degree. C. for 10 minutes in the atmosphere and
bonded together. The substrate 81 was also firmly bonded to the
rear plate 91 by means of frit glass (FIG. 9).
[0182] In FIG. 9, reference numeral denotes electron-emitting
devices and numerals 82 and 83 respectively denotes X-directional
wirings and Y-directional wirings.
[0183] While the fluorescent film 94 may be solely made of
fluorescent bodies if the image-forming apparatus is for black and
white pictures, firstly black stripes were arranged and then the
gaps separating the black stripes were filled with respective
fluorescent bodies for primary colors to produce a fluorescent film
94 in this experiment. The black stripes were made of a popular
material containing graphite as a principal ingredient. The
fluorescent bodies were applied to the glass substrate 93 by using
a slurry method.
[0184] A metal back 95 is normally arranged on the inner surface of
the fluorescent film 94. In this experiment, a metal back was
prepared by producing an Al film by vacuum deposition on the inner
surface of the fluorescent film 94 that had been smoothed in a
so-called filming process.
[0185] The face plate 96 may be additionally provided with
transparent electrodes (not shown) arranged close to the outer
surface of the fluorescent film 94 in order to improve the
conductivity of the fluorescent film 94, no such electrodes were
used in the experiment because the metal back proved to be
sufficiently conductive.
[0186] The fluorescent bodies were carefully aligned with the
respective electron-emitting devices before the above described
bonding operation.
[0187] The prepared glass container was then evacuated by means of
an exhaust pipe (not shown) and an exhaust pump to achieve a
sufficient degree of vacuum inside the container. Thereafter, the
thin films 2 of the electron-emitting devices 84 were subjected to
an electric forming operation, where a voltage was applied to the
device electrodes 5, 6 of the electron-emitting devices 84 by way
of the external terminals Dox1 through Doxm and Doy1 through Doyn
to produce an electron-emitting region 3 in each device. The
voltage used in the forming operation had a waveform same as the
one shown in FIG. 4B.
[0188] Referring to FIG. 4B, T1 and T2 were respectively 1
milliseconds and 10 milliseconds and the electric forming operation
was carried out in vacuum of a degree of approximately
1.times.10.sup.-5 torr.
[0189] Dispersed fine particles containing palladium as a principal
ingredient were observed in the electron-emitting region 3 of each
device that had been produced in the above process. The fine
particles had an average particle size of 30 angstroms.
[0190] Thereafter, the devices were subjected to a high resistance
activation process, where a voltage having a rectangular waveform
same as that of the voltage used in the forming operation and a
wave height of 14 V was applied to each device, observing the
device current If and the emission current Ie.
[0191] Finished electron-emitting devices 84 having an
electron-emitting region 3 were produced after the forming and
activation processes.
[0192] Subsequently, the enclosure was evacuated by means of an
oil-free ultra-high vacuum device to a degree of vacuum of
approximately 10.sup.-6 torr and then hermetically sealed by
melting and closing the exhaust pipe (not shown) by means of a gas
burner.
[0193] Finally, the apparatus was subjected to a getter process
using a high frequency heating technique in order to maintain the
degree of vacuum in the apparatus after the sealing operation.
[0194] The electron-emitting devices of the above image-forming
apparatus were then caused to emit electrons by applying a scan
signal and a modulation signal from a signal generating means (not
shown) through the external terminals Dx1 through Dxm and Dy1
through Dyn and the emitted electrons were accelerated by applying
a high voltage of 5 kV to the metal back 95 or the transparent
electrodes (not shown) via the high voltage terminal Hv so that
they collides with the fluorescent film 94 until the latter was
energized to emit light and produce an image. Both the device
current If and the emission current Ie of each device were similar
to those illustrated in FIG. 7 by solid lines to prove the device
operated stably from the initial stages. The emission current Ie
was such that it could sufficiently meet the requirement of
brightness of 100 fL to 150 fL of a television set.
Example 3
[0195] Specimens of electron-emitting device were prepared as in
the case of Example 1.
[0196] Each of the prepared electron-emitting devices had a device
width W2 of 300 .mu.m and the thin film 2 for an electron-emitting
region of the device had a film thickness of 10 nm and an electric
resistance per unit area of 5.times.10.sup.4.OMEGA./.quadrature..
Otherwise, the devices were same as their counterparts of Example
1.
[0197] Then, a gauging system as illustrated in FIG. 3 was set in
position and the inside was evacuated by means of a magnetic
levitation pump to a degree of vacuum of 2.times.10.sup.-8 torr.
Subsequently, a voltage was applied to the device electrodes 5, 6
for electrically energizing the device (electric forming process)
by the power source 31 provided there for applying a device voltage
Vf to the device. FIG. 4B shows the waveform of the voltage used
for the electric forming process.
[0198] In FIG. 4B, T1 and T2 respectively denote the pulse width
and the pulse interval of the applied pulse voltage, which were
respectively 1 millisecond and 10 milliseconds for the experiment.
The wave height (the peak voltage for the forming operation) of the
applied pulse voltage was increased stepwise with a step of 0.1 V.
During the forming operation, a resistance measuring pulse voltage
of 0.1 V was inserted during each T2 to determine the current
resistance of the device. The forming operation and the application
of the voltage to the device were terminated when the gauge for the
resistance measuring pulse voltages showed a reading of resistance
of approximately 1 M ohms. In the experiment, the reading of the
gauge for the forming voltage Vform was 5.1 V.
[0199] A prepared sample device was then subjected to an activation
process in an atmosphere containing acetone (having a vapor
pressure of 233 hPa at 20.degree. C.) to a pressure of
approximately 1.times.10.sup.-5 torr for 20 minutes. FIG. 4C shows
the waveform of the voltage applied to the device in the activation
process.
[0200] In FIG. 4C, T3 and T4 respectively denote the pulse width
and the pulse interval of the voltage wave, which were 10
microseconds and 10 milliseconds in the experiment. The wave height
of the rectangular wave was 14 V.
[0201] Thereafter, the vacuum chamber of the gauging system was
evacuated further to approximately 1.times.10.sup.-8 torr.
[0202] During the experiment, organic substances to be used for the
activation process were introduced via a feeding system (FIG. 12)
comprising a needle valve and the inside pressure of the vacuum
chamber was maintained to a substantially constant level.
[0203] Then, the performance of the device was determined by
applying a voltage of 1 kV to the anode in the gauging system,
where the device was separated from the anode by a distance H of 4
mm and the inside of the vacuum chamber was maintained to
1.times.10.sup.-8 torr.
[0204] It was observed that, when the device voltage was 14 V, the
device current and the emission current were respectively 2 mA and
1 .mu.A to prove an electron emission efficiency .theta. of 0.05%.
Table 1 shows the pulse width dependency of the device when the
voltage was 14 V, the pulse interval was 16.6 msec. and the pulse
width was 30 psec., 100 psec. and 300 psec.
Example 4
[0205] Device specimens were prepared under conditions same as
those of Example 3 except that n-dodecan (having a vapor pressure
of 0.1 hPa at 20.degree. C.) was used in place of acetone for the
activation process.
[0206] When one of the prepared devices was tested to see its If
and Ie as in the case of Example 3 above, the device current and
the emission current were respectively 2.2 mA and 1 .mu.A for a
device voltage of 14 V to prove an electron emission efficiency
.theta. of 0.045%. Table 1 shows the pulse width dependency of the
device when tested under the conditions same as those of Example
3.
Example 5
[0207] Device specimens were prepared under conditions same as
those of Example 3 except that the activation process was carried
out for two hours by using formaldehyde (having a vapor pressure of
4,370 hPa at 20.degree. C.) in place of acetone.
[0208] When one of the prepared devices was tested to see its If
and Ie as in the case of Example 3 above, the device current and
the emission current were respectively 1 mA and 0.2 .mu.A for a
device voltage of 14 V to prove an electron emission efficiency
.theta. of 0.02%.
Example 6
[0209] Device specimens were prepared under conditions same as
those of Example 3 except that n-hexane (having a vapor pressure of
160 hPa at 20.degree. C.) was used in place of acetone for the
activation process.
[0210] When one of the prepared devices was tested to see its If
and Ie as in the case of Example 3 above, the device current and
the emission current were respectively 1.8 mA and 0.8 .mu.A for a
device voltage of 14 V to prove an electron emission efficiency
.theta. of 0.044%. Table 1 shows the pulse width dependency of the
device when tested under the conditions same as those of Example
3.
Example 7-a
[0211] Device specimens were prepared under conditions same as
those of Example 3 except that n-undecane (having a vapor pressure
of 0.35 hPa at 20.degree. C.) was used in place of acetone for the
activation process.
[0212] When one of the prepared devices was tested to see its If
and Ie as in the case of Example 3 above, the device current and
the emission current were respectively 1.5 mA and 0.6 .mu.A for a
device voltage of 14 V to prove an electron emission efficiency
.theta. of 0.04%. Table 1 shows the pulse width dependency of the
device when tested under the conditions same as those of Example
3.
Example 7-b
[0213] Device specimens were prepared under conditions same as
those of Example 1 except organic substances were not introduced
into the gauging system and the activation process was carried out
in a vacuum/exhaust system having an oily atmosphere (connected
directly to a rotary pump and a turbo pump and capable of producing
a degree of vacuum of 5.times.10.sup.-7 torr).
[0214] When one of the prepared devices was tested to see its If
and Ie as in the case of Example 1 above, the device current and
the emission current were respectively 2.2 mA and 1.1 .mu.A for a
device voltage of 14 V to prove an electron emission efficiency
.theta. of 0.045%. Table 1 shows the pulse width dependency of the
device when tested under the conditions same as those of Example
3.
Example 8
[0215] In this example, an image-forming apparatus comprising a
large number of surface conduction electron-emitting devices
arranged to a simple matrix arrangement was prepared as in the case
of Example 2.
[0216] Firstly, a glass container containing an electron source
like that of Example 2 was produced and the glass container was
evacuated to a degree of vacuum of 1.times.10.sup.-6 torr via an
exhaust pipe (not shown) by means of an oil-free vacuum pump.
[0217] Thereafter, the thin films 2 of the electron-emitting
devices 84 were subjected to an electric forming operation, where a
voltage was applied to the device electrodes 5, 6 of the
electron-emitting devices 84 by way of the external terminals Dox1
through Doxm and Doy1 through Doyn to produce an electron-emitting
region 3 in each device. The voltage used in the forming operation
had a waveform same as the one shown in FIG. 4B.
[0218] Dispersed fine particles containing palladium as a principal
ingredient were observed in the electron-emitting region 3 of each
device that had been produced in the above process. The fine
particles had an average particle size of 30 angstroms.
[0219] Thereafter, the devices were subjected to an activation
process, where acetone was introduced into the glass container to a
pressure of 1.times.10.sup.-3 torr and a voltage was applied to the
device electrodes 5, 6 of each electron-emitting device 84 via
appropriate ones of the external terminals Dox1 through Doxm and
Doy1 through Doyn. FIG. 4C shows the waveform of the voltage used
for the activation process.
[0220] Subsequently, the acetone contained in the container was
evacuated to produce finished electron-emitting devices.
[0221] Then, the components of the apparatus was baked at
120.degree. C. for 10 hours in vacuum of a degree of approximately
1.times.10.sup.-6 torr and the enclosure was hermetically sealed by
melting and closing the exhaust pipe (not shown) by means of a gas
burner.
[0222] Finally, the apparatus was subjected to a getter process
using a high frequency heating technique in order to maintain the
degree of vacuum in the apparatus after the sealing operation. A
getter containing Ba as a principal component had been arranged in
a predetermined position (not shown) before hermetically sealing
the enclosure to form a film inside the enclosure through vapor
deposition.
[0223] The electron-emitting devices of the above image-forming
apparatus were then caused to emit electrons by applying a scan
signal and a modulation signal from a signal generating means (not
shown) through the external terminals Dx1 through Dxm and Dy1
through Dyn and the emitted electrons were accelerated by applying
a high voltage of 7 kV to the metal back 95 or the transparent
electrodes (not shown) via the high voltage terminal Hv so that
they collides with the fluorescent film 94 until the latter was
energized to emit light and produce an image.
Example 9
[0224] This example deals with an image-forming apparatus
comprising a large number of surface conduction electron-emitting
devices and control electrodes (grids).
[0225] Since an apparatus to be dealt in this example can be
prepared in a way as described above concerning the image-forming
apparatus of Example 2, the method of manufacturing the same will
not be described any further.
[0226] The configuration of the apparatus will be described in
terms of the electron source of the apparatus prepared by arranging
a number of surface conduction electron-emitting devices.
[0227] FIGS. 17 and 18 are schematic plan views of two different
substrates of electron source alternatively used in the
image-forming apparatus of Example 9.
[0228] Firstly referring to FIG. 17, S denotes an insulator
substrate typically made of glass and ES denotes an surface
conduction electron-emitting device arranged on the substrate S and
shown in a dotted circle, whereas E1 through E10 denote wiring
electrodes for wiring the surface conduction electron-emitting
devices, which are arranged in columns on the substrate along the
X-direction (hereinafter referred to as device columns). The
surface conduction electron-emitting devices of each device column
are electrically connected in parallel with each other by a pair of
wiring electrodes. (For instance, the devices of the first device
column are connected in parallel with each other by the wiring
electrodes E1 and E10.) In the apparatus of this example comprising
the above described electron source, the electron source can drive
any device column independently by applying an appropriate drive
voltage to the related wiring electrodes. More specifically, a
voltage exceeding the electron emission threshold level is applied
to the device columns to be driven to emit electrons, whereas a
voltage below the electron emission threshold level (e.g., 0 V) is
applied to the remaining device columns. (A drive voltage exceeding
the electron emission threshold level is referred to as VE[V]
hereinafter.)
[0229] In FIG. 18 illustrating another electron source that can be
used for this example, S denotes an insulator substrate typically
made of glass and ES denotes an surface conduction
electron-emitting device arranged on the substrate S and shown in a
dotted circle, whereas E'1 through E'6 denote wiring electrodes for
wiring the surface conduction electron-emitting devices, which are
arranged in columns on the substrate along the X-direction. The
surface conduction electron-emitting devices of each device column
are electrically connected in parallel with each other by a pair of
wiring electrodes. Additionally, in this alternative electron
source, a single wiring electrode is arranged between any two
adjacent device columns to serve for the both columns. For
instance, a common wiring electrode E'2 serves for both the first
device column and the second device column. This arrangement of
wiring electrodes is advantageous in that, if compared with the
arrangement of FIG. 17, the space separating any two adjacent
columns of surface conduction electron-emitting devices can be
significantly reduced.
[0230] In the apparatus of this example comprising the above
described electron source, the electron source can drive any device
column independently by applying an appropriate drive voltage to
the related wiring electrodes. More specifically, VE[V] is applied
to the device columns to be driven to emit electrons, whereas 0 V
is applied to the remaining device columns. For instance, only the
devices of the third column can be driven to operate by applying 0
V to the wiring electrodes E'1 through E'3 and VE[V] to the wiring
electrodes E'4 through E'6. Consequently, VE-0=VE[V] is applied to
the devices of the third column, whereas 0[V], 0-0=0[V] or
VE-VE=0[V], is applied to all the devices of the remaining columns.
Likewise, the devices of the second and the fifth columns can be
driven to operate simultaneously by applying 0[V] to the wiring
electrodes E'1, E'2 and E'6 and VE[V] to the wiring electrodes E'3,
E'4 and E'5. In this way, the devices of any device column of this
electron source can be driven selectively.
[0231] While each device column has twelve (12) surface conduction
electron-emitting devices arranged along the X-direction in the
electron sources of FIGS. 17 and 18, the number of devices to be
arranged in a device column is not limited thereto and a greater
number of devices may alternatively be arranged. Additionally,
while there are five (5) device columns in each of the electron
sources, the number of device columns is not limited thereto and a
greater number of device columns may alternatively be arranged.
[0232] Now, a panel type CRT incorporating an electron source of
the above described type will be described.
[0233] FIG. 19 is a schematic perspective view of a panel type CRT
incorporating an electron source as illustrated in FIG. 17. In FIG.
19, VC denotes a glass vacuum container provided with a face plate
FP for displaying images. A transparent electrode is arranged on
the inner surface of the face plate PH and red, green and blue
fluorescent members are applied onto the transparent electrode in
the form of a mosaic or stripes without interfering with each
other. To simplify the illustration, the transparent electrodes and
the fluorescent members are collectively indicated by PH in FIG.
19. A black matrix or black stripes known in the field of CRT may
be arranged to fill the blank areas of the transparent electrode
that are not occupied by the fluorescent matrix or stripes.
Similarly, a metal back layer of any known type may be arranged on
the fluorescent members. The transparent electrode is electrically
connected to the outside of the vacuum container by way of a
terminal EV so that an voltage may be applied thereto in order to
accelerate electron beams.
[0234] In FIG. 19, S denotes the substrate of the electron source
rigidly fitted to the bottom of the vacuum container VC, on which a
number of surface conduction electron-emitting devices are arranged
as described above by referring to FIG. 17. More specifically, a
total of 200 device columns, each having 200 devices, are arranged
on the substrate. Each device column is provided with a pair of
wiring electrodes and the wiring electrodes of the apparatus are
connected to the electrodes terminals Dp1 through Dp200 and Dm1
through Dm200 arranged on the respective opposite sides of the
panel in an alternate manner so that electric drive signals may be
applied to the devices from outside of the vacuum container.
[0235] In an experiment using a finished glass container VC (FIG.
19), the container was evacuated to a sufficient degree of vacuum
via an exhaust pipe (not shown) by means of an vacuum pump and,
thereafter, the electron-emitting devices ES were subjected to an
electric forming operation, where a voltage was applied to the
devices by way of the external terminals DP1 through DP200 and Dm1
through Dm200. The voltage used in the forming operation had a
waveform same as the one shown in FIG. 4B. In the experiment, T1
and T2 were respectively 1 milliseconds and 10 milliseconds and the
electric forming operation was carried out in vacuum of a degree of
approximately 1.times.10.sup.-5 torr.
[0236] Thereafter, the devices were subjected to an activation
process, where acetone was introduced into the glass container to a
pressure of 1.times.10.sup.-4 torr and a voltage was applied to the
electron-emitting devices ES via the external terminals Dp1 through
Dp200 and Dm1 through Dm200. Then, the acetone contained in the
container was evacuated to produce finished electron-emitting
devices.
[0237] Dispersed fine particles containing palladium as a principal
ingredient were observed in the electron-emitting region of each
device that had been produced in the above process. The fine
particles had an average particle size of 30 angstroms.
Subsequently, the vacuum system used for the experiment was
switched to an ultra-high vacuum system comprising an oil-free ion
pump. Thereafter, the components of the apparatus was baked at
120.degree. C. for a sufficient period of time in vacuum of a
degree of approximately 1.times.10.sup.-6 torr.
[0238] Then, the enclosure was hermetically sealed by melting and
closing the exhaust pipe (not shown) by means of a gas burner.
[0239] Finally, the apparatus was subjected to a getter process
using a high frequency heating technique in order to maintain the
degree of vacuum in the apparatus after the sealing operation and
finish the operation of preparing the image-forming apparatus.
[0240] Stripe-shaped grid electrodes GR are arranged between the
substrate S and the face plate. There are provided a total of 200
grid electrodes GR arranged in a direction perpendicular to that of
the device columns (or in the Y-direction) and each grid electrode
has a given number of openings Gh for allowing electron beams to
pass therethrough. More specifically, while a circular opening Gh
is typically provided for each surface conduction electron-emitting
device, the openings may alternatively be realized in the form of a
mesh. The grid electrodes are electrically connected to the outside
of the vacuum container via respective electric terminals G1
through G200. Note that the grid electrodes may be differently
arranged in terms of shape and location from those of FIG. 19 so
long as they can successfully modulate electron beams emitted from
the surface conduction electron-emitting devices. For instance,
they may be arranged around or in the vicinity of the surface
conduction electron-emitting devices.
[0241] The above described display panel comprises surface
conduction electron-emitting devices arranged in 200 device columns
and 200 grid electrodes to form an X-Y matrix of 200.times.200.
With such an arrangement, an image can be displayed on the screen
on a line by line basis by applying a modulation signal to the grid
electrodes for a single line of an image in synchronism with the
operation of driving (scanning) the surface conduction
electron-emitting devices on a column by column basis to control
the irradiation of electron beams onto the fluorescent film.
[0242] FIG. 20 is a block diagram of an electric circuit to be used
for driving the display panel of FIG. 19. In FIG. 20, the circuit
comprises the display panel 1000 of FIG. 19, a decode circuit 1001
for decoding composite image signals transmitted from outside, a
serial/parallel conversion circuit 1002, a line memory 1003, a
modulation signal generation circuit 1004, a timing control circuit
1005 and a scan signal generating circuit 1006. The electric
terminals of the display panel 1000 are connected to the related
circuits. Specifically, the terminal EV is connected to a voltage
source HV for generating an acceleration voltage of 10[kV] and the
terminals G1 through G200 are connected to the modulation signal
generation circuit 1004 while the terminals Dp1 through Dp200 are
connected to the scan signal generation circuit 1006 and the
terminals Dm1 through Dm200 are grounded.
[0243] Now, how each component of the circuit operates will be
described. The decode circuit 1001 is a circuit for decoding
incoming composite image signals such as NTSC television signals
and separating brightness signals and synchronizing signals from
the received composite signals. The former are sent to the
serial/parallel conversion circuit 1002 as data signals and the
latter are forwarded to the timing control circuit 1005 as Tsync
signals. In other words, the decode circuit 1001 rearranges the
values of brightness of the primary colors of RGB corresponding to
the arrangement of color pixels of the display panel 1000 and
serially transmits them to the serial/parallel conversion circuit
1002. It also extracts vertical and horizontal synchronizing
signals and transmits them to the timing control circuits 1005. The
timing control circuit 1005 generates various timing control
signals in order to coordinate the operational timings of different
components by referring to said synchronizing signal Tsync. More
specifically, it transmits Tsp signals to the serial/parallel
conversion circuit 1002, Tmry signals to the line memory 1003, Tmod
signals to the modulation signal generation circuit 1004 and Tscan
signals to the scan signal generation circuit 1005.
[0244] The serial/parallel conversion circuit 1002 samples
brightness signals Data it receives from the decode circuit 1001 on
the basis of timing signals Tsp and transmits them as 200 parallel
signals I1 through I200 to the line memory 1003. When the
serial/parallel conversion circuit 1002 completes an operation of
serial/parallel conversion on a set of data for a single line of an
image, the timing control circuit 1005 a write timing control
signal Tmry to the line memory 1003. Upon receiving the signal
Tmry, it stores the contents of the signals I1 through I200 and
transmits them to the modulation signal generation circuit 1004 as
signals I'1 through I'200 and holds them until it receives the next
timing control signal Tmry.
[0245] The modulation signal generation circuit 1004 generates
modulation signals to be applied to the grid electrodes of the
display panel 1000 on the basis of the data on the brightness of a
single line of an image it receives from the line memory 1003. The
generated modulation signals are simultaneously applied to the
modulation signal terminals G1 through G200 in correspondence to a
timing control signal Tmod generated by the timing control circuit
1005. While modulation signals typically operate in a voltage
modulation mode where the voltage to be applied to a device is
modulated according to the data on the brightness of an image, they
may alternatively operate in a pulse width modulation mode where
the length of the pulse voltage to be applied to a device is
modulated according to the data on the brightness of an image.
[0246] The scan signal generation circuit 1006 generates voltage
pulses for driving the device columns of the surface conduction
electron-emitting devices of the display panel 1000. It operates to
turn on and off the switching circuits it comprises according to
timing control signals Tscan generated by the timing control
circuit 1005 to apply either a drive voltage VE[V] generated by a
constant voltage source DV and exceeding the threshold level for
the surface conduction electron-emitting devices or the ground
potential level (0[V]) to each of the terminals Dp1 through
Dp200.
[0247] As a result of coordinated operations of the above described
circuits, drive signals are applied to the display panel 1000 with
the timings as illustrated in the graphs of FIGS. 21A through 21F.
FIGS. 21A through 21D show part of signals to be applied to the
terminals Dp1 through Dp200 of the display panel from the scan
signal generation circuit 1006. It is seen that a voltage pulse
having an amplitude of VE[V] is applied sequentially to Dp1, Dp2,
Dp3, . . . within a period of time for display a single line of an
image. On the other hand, since the terminals Dm1 through Dm200 are
constantly grounded and held to 0[V], the device columns are
sequentially driven by the voltage pulse to emit electron beams
from the first column.
[0248] In synchronism of this operation, the modulation signal
generation circuit 1004 applies moduation signals to the terminals
G1 through G200 for each line of an image with the timing as shown
by the dotted line in FIG. 21F. Modulation signals are sequentially
selected in synchornism with the selection of scan signals until an
entire image is displayed. By continuously repeating the above
operation, moving images are displayed on the display screen for
television.
[0249] A flat panel type CRT comprising an electron source of FIG.
17 has been described above. Now, a panel type CRT comprising an
electron source of FIG. 18 will be described below by referring to
FIG. 22.
[0250] The panel type CRT of FIG. 22 is realized by replacing the
electron source of the CRT of FIG. 19 with the one illustrated in
FIG. 18, which comprises an X-Y matrix of 200 columns of
electron-emitting devices and 200 grid electrodes. Note that the
200 columns of surface conduction electron-emitting devices are
respectively connected to 201 wiring electrodes E1 through E201
and, therefore, the vacuum container is provided with a total of
201 electrode terminals Ex1 through Ex201.
[0251] In an experiment using a finished glass container VC (FIG.
22), the container was evacuated to a sufficient degree of vacuum
via an exhaust pipe (not shown) by means of a vacuum pump and,
thereafter, the electron-emitting devices ES were subjected to an
electric forming operation, where a voltage was applied to the
devices by way of the external terminals Ex1 through Ex201. The
voltage used in the forming operation had a waveform same as the
one shown in FIG. 4B. In the experiment, T1 and T2 were
respectively 1 milliseconds and 10 milliseconds and the electric
forming operation was carried out in vacuum of a degree of
approximately 1.times.10-5 torr.
[0252] Thereafter, the devices were subjected to an activation
process, where acetone was introduced into the glass container to a
pressure of 1.times.10.sup.-4 torr and a voltage was applied to the
electron-emitting devices ES via the external terminals Dp1 through
Dp200 and Dm1 through Dm200. Then, the acetone contained in the
container was evacuated to produce finished electron-emitting
devices.
[0253] Dispersed fine particles containing palladium as a principal
ingredient were observed in the electron-emitting region of each
device that had been produced in the above process. The fine
particles had an average particle size of 30 angstroms.
Subsequently, the vacuum system used for the experiment was
switched to an ultra-high vacuum system comprising an oil-free ion
pump. Thereafter, the components of the apparatus was baked at
120.degree. C. for a sufficient period of time in vacuum of a
degree of approximately 1.times.10.sup.-6 torr.
[0254] Then, the enclosure was hermetically sealed by melting and
closing the exhaust pipe (not shown) by means of a gas burner.
[0255] Finally, the apparatus was subjected to a getter process
using a high frequency heating technique in order to maintain the
degree of vacuum in the apparatus after the sealing operation and
finish the operation of preparing the image-forming apparatus.
[0256] FIG. 23 shows a block diagram of a drive circuit for driving
the display panel 1008. This circuit has a configuration basically
same as that of FIG. 20 except the scan signal generation circuit
1007. The scan signal generation circuit 1007 applies either a
drive voltage VE[V] generated by a constant voltage source DV and
exceeding the threshold level for the surface conduction
electron-emitting devices or the ground potential level (0[V]) to
each of the terminals of the display panel. FIGS. 24A through 24I
show the timings with which certain signals are applied to the
display panel. The display panel operates to display an image with
the timing as illustrated in FIG. 24A as drive signals shown in
FIGS. 24B through 24E are applied to the electrode terminals Ex1
through Ex4 from the scan signal generation circuit 1007 and,
consequently, voltages as shown in FIGS. 24F through 24H are
sequentially applied to the corresponding columns of surface
conduction electron-emitting devices to drive the latter. In
synchronism with this operation, modulation signals are generated
by the modulation signal generation circuit 1004 with the timing as
shown in FIG. 24I to display images on the display screen.
[0257] An image-forming apparatus of the type realized in this
example operates very stably, showing full color images with
excellent gradation and contrast.
Example 10
[0258] FIG. 25 is a block diagram of the display apparatus
comprising an electron source realized by arranging a number of
surface conduction electron-emitting devices and a display panel
and designed to display a variety of visual data as well as
pictures of television transmission in accordance with input
signals coming from different signal sources. Referring to FIG. 25,
the apparatus comprises a display panel 25100, a display panel
drive circuit 25101, a display controller 25102, a multiplexer
25103, a decoder 25104, an input/output interface circuit 25105, a
CPU 25106, an image generation circuit 25107, image memory
interface circuits 25108, 25109 and 25110, an image input interface
circuit 25111, TV signal receiving circuits 25112 and 25113 and an
input section 25114. (If the display apparatus is used for
receiving television signals that are constituted by video and
audio signals, circuits, speakers and other devices are required
for receiving, separating, reproducing, processing and storing
audio signals along with the circuits shown in the drawing.
However, such circuits and devices are omitted here in view of the
scope of the present invention.)
[0259] Now, the components of the apparatus will be described,
following the flow of image data therethrough.
[0260] Firstly, the TV signal reception circuit 25113 is a circuit
for receiving TV image signals transmitted via a wireless
transmission system using electromagnetic waves and/or spatial
optical telecommunication networks. The TV signal system to be used
is not limited to a particular one and any system such as NTSC, PAL
or SECAM may feasibly be used with it. It is particularly suited
for TV signals involving a larger number of scanning lines
(typically of a high definition TV system such as the MUSE system)
because it can be used for a large display panel comprising a large
number of pixels. The TV signals received by the TV signal
reception circuit 25113 are fowarded to the decoder 25104.
[0261] Secondly, the TV signal reception circuit 25112 is a circuit
for receiving TV image signals transmitted via a wired transmission
system using coaxial cables and/or optical fibers. Like the TV
signal reception circuit 25113, the TV signal system to be used is
not limited to a particular one and the TV signals received by the
circuit are forwarded to the decoder 25104.
[0262] The image input interface circuit 25111 is a circuit for
receiving image signals forwarded from an image input device such
as a TV camera or an image pick-up scanner. It also forwards the
received image signals to the decoder 25104.
[0263] The image memory interface circuit 25110 is a circuit for
retrieving image signals stored in a video tape recorder
(hereinafter referred to as VTR) and the retrieved image signals
are also forwarded to the decoder 25104.
[0264] The image memory interface circuit 25109 is a circuit for
retrieving image signals stored in a video disc and the retrieved
image signals are also forwarded to the decoder 25104.
[0265] The image memory interface circuit 25108 is a circuit for
retrieving image signals stored in a device for storing still image
data such as so-called still disc and the retrieved image signals
are also forwarded to the decoder 25104.
[0266] The input/output interface circuit 25105 is a circuit for
connecting the display apparatus and an external output signal
source such as a computer, a computer network or a printer. It
carries out input/output operations for image data and data on
characters and graphics and, if appropriate, for control signals
and numerical data between the CPU 25106 of the display apparatus
and an external output signal source.
[0267] The image generation circuit 25107 is a circuit for
generating image data to be displayed on the display screen on the
basis of the image data and the data on characters and graphics
input from an external output signal source via the input/output
interface circuit 25105 or those coming from the CPU 25106. The
circuit comprises reloadable memories for storing image data and
data on characters and graphics, read-only memories for storing
image patterns corresponding given character codes, a processor for
processing image data and other circuit components necessary for
the generation of screen images.
[0268] Image data generated by the circuit for display are sent to
the decoder 25104 and, if appropriate, they may also be sent to an
external circuit such as a computer network or a printer via the
input/output interface circuit 25105.
[0269] The CPU 25106 controls the display apparatus and carries out
the operation of generating, selecting and editing images to be
displayed on the display screen.
[0270] For example, the CPU 25106 sends control signals to the
multiplexer 25103 and appropriately selects or combines signals for
images to be displayed on the display screen. At the same time it
generates control signals for the display panel controller 25102
and controls the operation of the display apparatus in terms of
image display frequency, scanning method (e.g., interlaced scanning
or non-interlaced scanning), the number of scanning lines per frame
and so on.
[0271] The CPU 25106 also sends out image data and data on
characters and graphic directly to the image generation circuit
25107 and accesses external computers and memories via the
input/output interface circuit 25105 to obtain external image data
and data on characters and graphics. The CPU 25106 may additionally
be so designed as to particpate other operations of the display
apparatus including the operation of generating and processing data
like the CPU of a personal computer or a word processor. The CPU
25106 may also be connected to an external computer network via the
input/output interface circuit 25105 to carry out computations and
other operations, cooperating therewith.
[0272] The input section 25114 is used for forwarding the
instructions, programs and data given to it by the operator to the
CPU 25106. As a matter of fact, it may be selected from a variety
of input devices such as keyboards, mice, joy sticks, bar code
readers and voice recognition devices as well as any combinations
thereof.
[0273] The decoder 25104 is a circuit for converting various image
signals input via said circuits 25107 through 25113 back into
signals for three primary colors, luminance signals and I and Q
signals. Preferably, the decoder 25104 comprises image memories as
indicated by a dotted line in FIG. 25 for dealing with television
signals such as those of the MUSE system that require image
memories for signal conversion. The provision of image memories
additionally facilitates the display of still images as well as
such operations as thinning out, interpolating, enlarging,
reducing, synthesizing and editing frames to be optionally carried
out by the decoder 25104 in cooperation with the image generation
circuit 25107 and the CPU 25106.
[0274] The multiplexer 25103 is used to appropriately select images
to be displayed on the display screen according to control signals
given by the CPU 25106. In other words, the multiplexer 25103
selects certain converted image signals coming from the decoder
25104 and sends them to the drive circuit 25101. It can also divide
the display screen in a plurality of frames to display different
images simultaneously by switching from a set of image signals to a
different set of image signals within the time period for
displaying a single frame.
[0275] The display panel controller 25102 is a circuit for
controlling the operation of the drive circuit 25101 according to
control signals transmitted from the CPU 25106.
[0276] Among others, it operates to transmit signals to the drive
circuit 25101 for controlling the sequence of operations of the
power source (not shown) for driving the display panel in order to
define the basic operation of the display panel. It also transmits
signals to the drive circuit 25101 for controlling the image
display frequency and the scanning method (e.g., interlaced
scanning or non-interlaced scanning) in order to define the mode of
driving the display panel.
[0277] If appropriate, it also transmits signals to the drive
circuit 25101 for controlling the quality of the images to be
displayed on the display screen in terms of luminance, contrast,
color tone and sharpness.
[0278] The drive circuit 25101 is a circuit for generating drive
signals to be applied to the display panel 25100. It operates
according to image signals coming from said multiplexer 25103 and
control signals coming from the display panel controller 25102.
[0279] A display apparatus according to the invention and having a
configuration as described above and illustrated in FIG. 25 can
display on the display panel 25100 various images given from a
variety of image data sources. More specifically, image signals
such as television image signals are converted back by the decoder
25104 and then selected by the multiplexer 25103 before sent to the
drive circuit 25101. On the other hand, the display controller
25102 generates control signals for controlling the operation of
the drive circuit 25101 according to the image signals for the
images to be displayed on the display panel 25100. The drive
circuit 25101 then applies drive signals to the display panel 25100
according to the image signals and the control signals. Thus,
images are displayed on the display panel 25100. All the above
described operations are controlled by the CPU 25106 in a
coordinated manner.
[0280] The above described display apparatus can not only select
and display particular images out of a number of images given to it
but also carry out various image processing operations including
those for enlarging, reducing, rotating, emphasizing edges of,
thinning out, interpolating, changing colors of and modifying the
aspect ratio of images and editing operations including those for
synthesizing, erasing, connecting, replacing and inserting images
as the image memories incorporated in the decoder 25104, the image
generation circuit 25107 and the CPU 25106 participate such
operations. Although not described with respect to the above
embodiment, it is possible to provide it with additional circuits
exclusively dedicated to audio signal processing and editing
operations.
[0281] Thus, a display apparatus according to the invention and
having a configuration as described above can have a wide variety
of industrial and commercial applications because it can operate as
a display apparatus for television broadcasting, as a terminal
apparatus for video teleconferencing, as an editing apparatus for
still and movie pictures, as a terminal apparatus for a computer
system, as an OA apparatus such as a word processor, as a game
machine and in many other ways.
[0282] It may be needless to say that FIG. 25 shows only an example
of possible configuration of a display apparatus comprising a
display panel provided with an electron source prepared by
arranging a number of surface conduction electron-emitting devices
and the present invention is not limited thereto. For example, some
of the circuit components of FIG. 25 may be omitted or additional
components may be arranged there depending on the application. For
instance, if a display apparatus according to the invention is used
for visual telephone, it may be appropriately made to comprise
additional components such as a television camera, a microphone,
lighting equipment and transmission/reception circuits including a
modem.
[0283] Since a display apparatus according to the invention
comprises a display panel that is provided with an electron source
prepared by arranging a large number of surface conduction
electron-emitting device and hence adaptable to reduction in the
depth, the overall apparatus can be made very thin. Additionally,
since a display panel comprising an electron source prepared by
arranging a large number of surface conduction electron-emitting
devices is adapted to have a large display screen with an enhanced
luminance and provide a wide angle for viewing, it can offer really
impressive scenes to the viewers with a sense of presence.
[0284] [Advantages of the Invention]
[0285] As described above, the present invention provides a method
of manufacturing a surface conduction electron-emitting device
comprising a pair of oppositely disposed device electrodes and a
thin film including an electron-emitting region arranged on a
substrate, wherein it comprises at least steps of forming a pair of
electrodes, forming a thin film (including an electron-emitting
region), conducting an electric forming process and conducting an
activation process so that the electron emission performance of the
device that has hitherto been undeterminable can be strictly
controlled as the forming process and the activation process are
conducted in two separate steps and a coat containing carbon in the
form of graphite, amorphous carbon or a mixture thereof as a
principal ingredient is formed on and around the electron-emitting
region under a controlled manner.
[0286] Preferably, the activation process comprises steps of
forming a coat containing carbon as a principal ingredient on the
thin film and applying a voltage exceeding the
voltage-controlled-negative-resistance level to the pair of
electrodes of the device so that the coat containing carbon as a.
principal ingredient may be formed on the high voltage side from
part of the electron-emitting region. With such an arrangement, the
produced electron-emitting device can operate stably from the
initial stages of operation with a low device current and a high
efficiency.
[0287] According to the invention, there is also provided an
electron source designed to emit electrons in accordance to input
signals and comprising a plurality of electron-emitting devices of
the above described type on a substrate, wherein the
electron-emitting devices are arranged in rows, each device being
connected to wirings at opposite ends, and a modulation means is
provided for them or, alternatively, the pairs of device electrodes
of the electron-emitting devices are respectively connected to m
insulated X-directional wirings and n insulated Y-directional
wirings, the electron-emitting devices being arranged in rows
having a plurality of devices. With such an arrangement, an
electron source according to the invention can be manufactured at
low cost with a high yield. Additionally, an electron source
according to the invention operates highly efficiently in an energy
saving manner so that it alleviates the load imposed on the
circuits that are peripheral to it.
[0288] According to the invention, there is also provided an
image-forming apparatus for forming images according to input
signals, said apparatus comprising at least image-forming members
and an electron source according to the invention. Such an
apparatus can ensure efficient and stable emission of electrons to
be carried out in a controlled manner. If, for example, the
image-forming members are fluorescent members, the image-forming
apparatus may make a flat color television set that can display
high quality images with a low energy consumption level.
1 TABLE 1 Device current (mA) Emission current (.mu.A) Pulse width
30 .mu.s 100 .mu.s 300 .mu.s 30 .mu.s 100 .mu.s 300 .mu.s Example 3
1.8 2.0 2.0 0.9 0.9 1.0 acetone Example 6 1.7 1.7 1.8 0.7 0.7 0.8
n-hexane Example 7-a 1.4 1.4 1.5 0.5 0.6 0.6 n-undecane Example 4
2.6 2.4 2.2 1.4 1.2 1.0 n-dodecane Example 7-b 2.9 2.5 2.2 1.7 1.4
1.1 oil
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